Physics Final Exam Review 2007
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A clown is walking west on board a train moving east at high speed. How is the clown moving according to a cardiologist standing at the platform while the train passes?
Relative motion
Answer: 2
1. East, at the same speed as the train 2. East, slightly slower than the train 3. West 4. The clown is not moving according to the cardiologist
Motion depends on the observer. In this case, if you use the telescope test you can tell the clown is moving east from the perspective of the cardiologist.
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A hockey puck glides across the ice at a constant speed. In which direction(s) are forces being exerted on the hockey puck?
Motion with constant velocity
Answer: 5 An object moving at constant velocity has a net force of zero. There is no unbalanced force in the direction of motion
1. Up 2. Down 3. In the direction of its motion 4. Opposite the direction of its motion 5. Both 1 & 2 6. 1, 2, and 3
Fice on puck
puck Fearth on puck 0
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A baseball has just left the hand that threw it straight upward. What is the direction of the net force on the ball?
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Motion with constant velocity
Answer: 2 The ball has left the hand. The hand is not touching. There is no force exerted by the hand.
1. Up 2. Down 3. There is no net force exerted on the ball 4. There is not enough information to tell
ball
Fearth on ball
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The only force on the ball is down. That's why the ball is accelerating in the down direction
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A brick rests on a table which sits on the floor. Which of these would NOT appear on a free body diagram for the table? 1. 2. 3. 4. 5.
Force of brick on table Force of earth on table Force of table on earth Force of floor on table ALL of these would appear
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Force
Answer: 3 A free body diagram for the table shows forces exerted on the table.
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Ffloor on table
table Fbrick on table
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Which of these situations does NOT include a force exerted by each underlined object on the other?
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Answer: 2 A force is a push or pull between two objects. The only objects that can push or pull without touching are: • the earth • a charged object • a magnetic object.
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Chris drives 30km to work in 30 minutes. Grey drives 10km to work in 12 minutes. Who has a faster average speed? 1. 2. 3. 4.
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Speed
Answer: 1 Speed = how far / how long
Chris Grey They are the same Answer cannot be determined
Chris: ∆x ∆t 30km = 30min = 1km/min
v=
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Force
1. A book rests on the surface of a desk 2. A ball flies into the air after leaving the hand that threw it 3. A wagon is pulled at constant speed by a rope 4. A brick falls freely toward the earth 5. All of these describe a force
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Fearth on table
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Grey: ∆x ∆t 10 km = 12 min =< 1km/min
v=
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Chris and Charles both start moving from rest when the light turns green. Ten seconds later, Chris is going 60 mph and Charles is going 55 mph. Which is true? 1. Chris and Charles were never at the same position 2. Chris and Charles were never going the same speed at the same time 3. Chris has a greater average acceleration than Charles 4. All of these statements are true 13
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We choose the coordinate axis or use the axis specified 100
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Sometimes we just talk about positive, negative, and zero
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An axis has an origin and a scale in the positive and negative direction
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Speed
Answer: 5 Acceleration is change in velocity
1. The position of the object must be negative 2. The velocity of the object must be negative 3. The acceleration of the object must be negative 4. The acceleration of the object must be zero 5. Both 2 and 4
Constant velocity = no acceleration = no net force Going in the negative direction = negative velocity Speeding up in the negative direction = negative acceleration
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Which statement about the quantity "net force" is NOT correct? 1. An object always moves in the direction of the net force exerted on it 2. The net force is the total of all the forces exerted on an object of interest 3. If all forces exerted on an object are balanced by other forces, the net force on the object is zero 4. An object can be in motion with a net force of zero 5. More than one of these is NOT correct 17
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Position x is where the object is located on the coordinate axis
If an object has a constant speed in the negative direction, which of the following is true?
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Answer: 4
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Net force
Answer: 1 Definition: the total of all forces exerted on an object Zero net force = no forces at all OR all forces balanced by other forces No net force = no CHANGE IN motion = not moving OR moving at constant velocity
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3
Which of these pairs of forces is an example of Newton's third law FA on B = –FB on A? 1. 2.
3. 4.
5.
Answer: 2 FA on B = − FB on A
You are seated on a bench. The earth exerts a force on you, and the bench exerts a force on you. A pen sits on a desk. The desk exerts a force on the pen, and the pen exerts a force on the desk. You pull on a rope. The rope pulls on a wagon. A book slides across a tabletop. The book exerts a downward force on the table, and the table exerts a frictional force to slow the book. Both 2 and 4
If object A exerts a force on object B, object B exerts an equal force on object A in the opposite direction
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Circular motion
Answer: 3 An object moving in a circular path (or part of a circular path) has a net force toward the center of the circle
1. In line with the circumference of the circle 2. Outward from the circle 3. Inward toward your feet 4. At a tangent to the circle 5. Backwards and outwards
Net force to center? It will move in a circle Moving in a circle? There is a net force to the center
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It is possible for two cars to have the same speed but different velocities?
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Speed and velocity
Answer: 4 Speed means how fast you are going
1. Yes, if the cars have different masses 2. Yes, if the cars start from different points 3. Yes, if the cars have different engines 4. Yes, if the cars are going in different directions 5. No, it is not possible
Velocity means how fast you are going and in what direction 50mph east and 50mph northeast: same speed different velocity
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Fman on wagon
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A battery-powered hover cart glides toward you across the floor. You have a stick. How do you need to tap the cart to make it move in a circle around your feet?
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wagon
man
Fwagon on man
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Newton's third law
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4
What force(s) cause the earth to rotate around the sun once every year?
Circular motion
Answer: 2 Moving in a circle? There is a net force to the center
1. The force of the earth's movement 2. The force of the sun's gravitational attraction 3. The force of the sun's solar wind 4. The force of swirling etheric vortices 5. Both 1 and 2
In this case, the force is the gravitational attraction between the earth and the sun No force is required to keep the earth moving
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A stationary soccer ball is kicked and rolls away over the grass. What quantity does it have after the kick that it did not have before? 1. 2. 3. 4. 5.
Answer: 5 The momentum of an object is a equal to its mass times its velocity
p = mv
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A Radio Flyer wagon carrying one school book rolls along a level sidewalk. Which other Radio Flyer would have MORE momentum?
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Momentum
Answer: 3
p = mv
1. A wagon loaded with school books, not moving 2. An empty wagon rolling at the same speed 3. An identical wagon rolling faster 4. None of these
Momentum increases when velocity increases or when mass increases
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Momentum
Mass Force Inertia Impulse Momentum
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Cart A and cart B roll toward each other on a smooth track and collide. What quantity will always be the same before and after the collision? 1. The force of A plus the force of B 2. The speed of A plus the speed of B 3. The velocity of A plus the velocity of B 4. The total momentum of both carts 5. All these quantities stay the same 31
Answer: 4
pbefore = pafter mA vA1 + mB vB1 = mA vA 2 + mB vB2 Although velocities can change during a collision or explosion, the total amount of momentum remains the same
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5
What is the term we use when the total amount of some quantity remains the same before and after an event? 1. 2. 3. 4. 5. 6. 7.
Momentum
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Conservation
Answer: 5 If the total amount of some quantity remains the same, even though it can change form or be transferred, we say that it is conserved.
Coincidence Convergence Congruence Conditioning Conservation Constantiation Cromulence
In your personal finances, your net worth is conserved even though you may take money out of your bank account and put it in your pocket. This is always true after a visit to the ATM right?
$ wallet before + $ ATM before = $ wallet after + $ ATM after 0
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Chris throws a ball up in the air. If we say that the ball and the earth are the system, what does that mean?
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System
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Answer: 3 system
1. 2. 3.
4.
The motion of the ball is determined by the earth The ball and earth obey rules of physics We are considering the ball and earth separately from Chris and other objects Nothing else interacts with the ball and the earth
The system is the part of the world we are interested in at the moment. It's a choice. The environment is everything outside the system. We draw the system with a circle around it. 0
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environment
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What do we call a force exerted by an object outside the system on an object inside the system? 1. 2. 3. 4. 5.
System
Answer: 4
Work Energy Interference External interaction Extrinsic force
ball and ramp: internal interaction
ramp and table: external interaction
An internal interaction is between objects in the system. An external interaction involves an object outside the system. 0 37
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Consider a system that includes a ball at the top of a ramp, the ramp, and the earth. What is an example of a process that could occur in this system? 1. The system is considered at an instant in time 2. The ball rolls to the bottom of the ramp 3. A hand holds the ball in place at the top of the ramp 4. The system is analyzed using physics rules 39
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Answer: 2 initial state
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Answer: 4 In any isolated system, mass never appears or disappears although it may change form. The same is true for energy and momentum.
initial state
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final state
Principles of conservation
Mass Energy Momentum Velocity
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Energy
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A process is when the system changes from one state to another state over a period of time. The process is a change from an initial state to a final state
In any system of objects that does not interact with the environment, which of the following quantities is NOT always conserved? 1. 2. 3. 4.
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final state
Bonus question: is this an isolated system?
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What is the real name of "Chalk smashing potential"?
Energy
Answer: 3 brick
1. 2. 3. 4. 5. 6.
Momentum Work Energy Temperature Inertia Height
earth
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We used the idea of "chalk smashing potential" as a way to visualize the concept of energy. A system can contain energy in many different forms. Energy is, technically, the ability to do stuff.
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An object is raised above the surface of the earth. What kind of energy has been increased in the system of object and earth?
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Gravitational Potential Energy
Answer: 4
Kinetic energy Vertical energy Potential energy Gravitational potential energy 5. Internal energy
brick
1. 2. 3. 4.
earth
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When an object and the earth are separated against their mutual attraction they gain more ability to do stuff if released. For a system to contain gravitational potential energy, the earth must be included in the system.
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A fast- moving racecar slows down on a level track. Which statement is correct about the system that includes racecar, track, and earth? 1. Gravitational potential energy has decreased 2. Kinetic energy has decreased 3. Kinetic energy has increased 4. Kinetic energy has not changed 5. More than one of these is true 47
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Kinetic Energy
Answer: 3 The energy of a moving object is called kinetic energy. If the object moves faster its kinetic energy increases
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What is the term for an external interaction that changes the total amount of energy in a system?
Work
Answer: 4 brick
1. 2. 3. 4. 5.
Non-conservative force Impulse External influence Work Environmental factor
positive work
brick
When something from outside the system causes the total energy in the system to change, this is work If the total energy in the system increases we say positive work has been done 0
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Which situation describes a transformation of energy from one form to another?
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Energy Type of energy in the system
A block is supported 2m above the ground by a wire 2. A block is supported 2m above the ground by a stretched spring 3. A ball rolls at constant speed across a level surface 4. A ball is released from rest at the top of a hill, and rolls down 5. More than one of these decsribes a transformation of energy
1.
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Answer: 4 Increases when:
Decreases when:
Gravitational Potential Energy
System object moves higher
System object moves lower
K
Kinetic Energy
System object moves faster
System object moves slower
Something elastic is stretched or compressed from its rest position
Us
Elastic Potential Energy
Object is stretched or compressed more
Object is stretched or compressed less
Electric charges are separated
Uq
Electrostatic Potential Energy
More charges are separated
Fewer charges are separated
Symbol
Name
Something is elevated above the earth
Ug
Something is moving
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Which statement describes an observation about fire walking?
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Observation
Answer: 1
1.
Some people walk on burning hot coals without injury 2. Evaporating perspiration cools the soles of the feet 3. The soles of the feet are protected by a layer of ash 4. Mental concentration and spiritual powers protect the feet 5. Some people will believe anything you tell them
An observation is a report of what you can see or measure, without any attempt to explain. Think of a radio announcer at a ballgame or a crime scene investigator trying to describe accurately and neutrally what she sees.
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earth
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Which is a possible explanation for why people can walk on burning coals without injury? 1. Some people have a power of mind over matter 2. Evaporating perspiration protects the feet 3. A layer of ash insulates the feet 4. The coals are not really hot 5. All but 4 55
Think of how you could explain the phenomenon using what you know. You may need to propose a new idea to explain what you see -- maybe even magic.
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How would we investigate possible explanations for why some people can walk on burning hot coals without injury?
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Testing
Answer: 4 Ideas are tested by trying to show they are false.
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Idea: "This is a good used car for me to buy" Prediction: "If I turn the key, the car will start" Test: Turn the key
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How could you test the idea that mental concentration protects the feet during a firewalk?
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Testing
Answer: 4
1.
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Use the idea to make a prediction. If the prediction does not come true, the explanation is no good.
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Ask many experimental subjects to attempt a firewalk using mental concentration 2. Ask many experimental subjects to attempt other feats using mental concentration 3. Ask subjects to describe how mental concentration works 4. Ask many experimental subjects to attempt a firewalk without using mental concentration
Answer: 5 An explanation is an idea that could possibly account for what you have observed.
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1. Ask people how they are able to perform this feat 2. Look for evidence to confirm our ideas 3. Find out what the experts think 4. List all possible explanations and try to disprove each one 5. Observe similar odd feats like fire-breathing
Explanations
The only definite conclusion is disproof. If you can firewalk without mental concentration, mental concentration is not necessary to walk over hot coals Idea: "This is a good used car for me to buy" Car starts: idea may be correct Tires are good: idea may be correct Brakes work: idea may be correct Hole in the floor: idea is NOT CORRECT 0
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Keep testing until disproved or satisfied with maybe!
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Which observation is NOT explained by the idea that liquids and gases are composed of a large number of tiny particles in continuous random motion? 1. Alcohol gradually disappears from paper 2. A balloon full of air has a round shape 3. Open a bottle of perfume and soon you will smell it 4. Milk eventually mixes into coffee even without stirring 5. ALL of these can be so explained 61
Kinetic Molecular Theory of Matter
Answer: 5 Tiny molecules are in constant random motion. Alcohol molecules jump off the paper sooner or later Air molecules collide continuously with the walls of a balloon Perfume molecules move among air molecules, across the room to your nose Milk and coffee molecules jostle and intermingle like dancers in a crowded club
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Which statement is NOT true about an inflated balloon?
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Kinetic Molecular Theory of Matter
Answer: 1 1. Air molecules are packed together tightly inside 2. Air molecules are continually colliding with the inside walls of the balloon 3. Air molecules are continually colliding with the outside walls of the balloon 4. The area inside the balloon 0 is mostly empty space 1 635. ALL of these are true D'Amato PTHS 2007
Air and other gases at room temperature are mostly empty space. Molecules move at high speeds through empty space, colliding with all surfaces and sometimes with each other These collisions cause gases to exert pressure on all surfaces A large number of tiny collisions feels like a continuous force 0
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Which will NOT occur when the temperature of a box of gas is increased, according to our model? 1. Gas molecules will move more quickly 2. Gas molecules will collide with the walls of the box more often 3. Gas molecules will collide harder with the walls of the box 4. The amount of empty space inside the box will decrease 5. The pressure inside the box will increase 65
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Fluids at rest
Answer: 4 An increase in temperature means an increase in the speed of the rapidly moving microscopic particles In gas, this means more and harder collisions with surfaces including the walls of the container In liquid, this means its more likely that liquid molecules will escape each other and become gas
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Consider four similar containers of liquid. In which will you measure the greatest pressure at the bottom of the ruler? 1.
Fluids at rest
Answer: 5
2.
Pressure in a liquid or gas is exerted because of the force required to support the fluid above. The depth below the surface of the fluid is the only factor that influences the pressure at any point flask
bucket
3.
4.
5. All pressures are the same
cylinder
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funnel
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Consider the point indicated in an open container of liquid. In which direction is the pressure greatest? 1. 2. 3. 4. 5.
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Fluids at rest
Answer: 5 At any small point, pressure is the same in all directions.
Direction 1 Direction 2 Direction 3 Direction 4 All the same
We explain this by saying that microscopic particles are colliding from all directions.
1
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Compare the pressure exerted by the liquid on the submerged block X at point A and point B 1. 2. 3. 4.
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Fluids at rest
Answer: 2 Deeper in the fluid means more pressure.
A is greater than B B is greater than A A is equal to at B There is not enough information to compare
Pressure is the same in all directions at a given depth.
A X
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If block X is sinking in the fluid, what is the direction of the force exerted on the block by the liquid? 1. 2. 3. 4.
Fluids at rest
Answer: 1 There is always an upward force exerted by the fluid on a submerged or a partially submerged object
up down none There is not enough information to tell
But that does not mean the object will always float! Why not? Fliquid on block
block X
Does this block float or sink?
X
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Fearth on block 4
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Relative motion
Answer: 2
1. East, at the same speed as the train 2. East, slightly slower than the train 3. West 4. The clown is not moving according to the cardiologist
Motion depends on the observer. In this case, if you use the telescope test you can tell the clown is moving east from the perspective of the cardiologist.
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A hockey puck glides across the ice at a constant speed. In which direction(s) are forces being exerted on the hockey puck?
Motion with constant velocity
Answer: 5 An object moving at constant velocity has a net force of zero. There is no unbalanced force in the direction of motion
1. Up 2. Down 3. In the direction of its motion 4. Opposite the direction of its motion 5. Both 1 & 2 6. 1, 2, and 3
Fice on puck
puck Fearth on puck 0
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A baseball has just left the hand that threw it straight upward. What is the direction of the net force on the ball?
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Motion with constant velocity
Answer: 2 The ball has left the hand. The hand is not touching. There is no force exerted by the hand.
1. Up 2. Down 3. There is no net force exerted on the ball 4. There is not enough information to tell
ball
Fearth on ball
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The only force on the ball is down. That's why the ball is accelerating in the down direction
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A brick rests on a table which sits on the floor. Which of these would NOT appear on a free body diagram for the table? 1. 2. 3. 4. 5.
Force of brick on table Force of earth on table Force of table on earth Force of floor on table ALL of these would appear
0
0
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Force
Answer: 3 A free body diagram for the table shows forces exerted on the table.
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Ffloor on table
table Fbrick on table
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Which of these situations does NOT include a force exerted by each underlined object on the other?
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Answer: 2 A force is a push or pull between two objects. The only objects that can push or pull without touching are: • the earth • a charged object • a magnetic object.
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Chris drives 30km to work in 30 minutes. Grey drives 10km to work in 12 minutes. Who has a faster average speed? 1. 2. 3. 4.
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Speed
Answer: 1 Speed = how far / how long
Chris Grey They are the same Answer cannot be determined
Chris: ∆x ∆t 30km = 30min = 1km/min
v=
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Force
1. A book rests on the surface of a desk 2. A ball flies into the air after leaving the hand that threw it 3. A wagon is pulled at constant speed by a rope 4. A brick falls freely toward the earth 5. All of these describe a force
9
Fearth on table
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Grey: ∆x ∆t 10 km = 12 min =< 1km/min
v=
0 4
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2
Chris and Charles both start moving from rest when the light turns green. Ten seconds later, Chris is going 60 mph and Charles is going 55 mph. Which is true? 1. Chris and Charles were never at the same position 2. Chris and Charles were never going the same speed at the same time 3. Chris has a greater average acceleration than Charles 4. All of these statements are true 13
−
+
We choose the coordinate axis or use the axis specified 100
0
0
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2
3
Sometimes we just talk about positive, negative, and zero
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4
10
An axis has an origin and a scale in the positive and negative direction
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Speed
Answer: 5 Acceleration is change in velocity
1. The position of the object must be negative 2. The velocity of the object must be negative 3. The acceleration of the object must be negative 4. The acceleration of the object must be zero 5. Both 2 and 4
Constant velocity = no acceleration = no net force Going in the negative direction = negative velocity Speeding up in the negative direction = negative acceleration
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Which statement about the quantity "net force" is NOT correct? 1. An object always moves in the direction of the net force exerted on it 2. The net force is the total of all the forces exerted on an object of interest 3. If all forces exerted on an object are balanced by other forces, the net force on the object is zero 4. An object can be in motion with a net force of zero 5. More than one of these is NOT correct 17
0
Position x is where the object is located on the coordinate axis
If an object has a constant speed in the negative direction, which of the following is true?
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Answer: 4
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D'Amato PTHS 2007
Net force
Answer: 1 Definition: the total of all forces exerted on an object Zero net force = no forces at all OR all forces balanced by other forces No net force = no CHANGE IN motion = not moving OR moving at constant velocity
0
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0
0
0
2
3
4
0 5
18
D'Amato PTHS 2007
3
Which of these pairs of forces is an example of Newton's third law FA on B = –FB on A? 1. 2.
3. 4.
5.
Answer: 2 FA on B = − FB on A
You are seated on a bench. The earth exerts a force on you, and the bench exerts a force on you. A pen sits on a desk. The desk exerts a force on the pen, and the pen exerts a force on the desk. You pull on a rope. The rope pulls on a wagon. A book slides across a tabletop. The book exerts a downward force on the table, and the table exerts a frictional force to slow the book. Both 2 and 4
If object A exerts a force on object B, object B exerts an equal force on object A in the opposite direction
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0
0
0
2
3
4
5
20
D'Amato PTHS 2007
Circular motion
Answer: 3 An object moving in a circular path (or part of a circular path) has a net force toward the center of the circle
1. In line with the circumference of the circle 2. Outward from the circle 3. Inward toward your feet 4. At a tangent to the circle 5. Backwards and outwards
Net force to center? It will move in a circle Moving in a circle? There is a net force to the center
0 1 D'Amato PTHS 2007
0
0
0
2
3
4
0 5
It is possible for two cars to have the same speed but different velocities?
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Speed and velocity
Answer: 4 Speed means how fast you are going
1. Yes, if the cars have different masses 2. Yes, if the cars start from different points 3. Yes, if the cars have different engines 4. Yes, if the cars are going in different directions 5. No, it is not possible
Velocity means how fast you are going and in what direction 50mph east and 50mph northeast: same speed different velocity
0 23
Fman on wagon
0
A battery-powered hover cart glides toward you across the floor. You have a stick. How do you need to tap the cart to make it move in a circle around your feet?
21
wagon
man
Fwagon on man
0 19
Newton's third law
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0
0
0
2
3
4
0 5
24
D'Amato PTHS 2007
4
What force(s) cause the earth to rotate around the sun once every year?
Circular motion
Answer: 2 Moving in a circle? There is a net force to the center
1. The force of the earth's movement 2. The force of the sun's gravitational attraction 3. The force of the sun's solar wind 4. The force of swirling etheric vortices 5. Both 1 and 2
In this case, the force is the gravitational attraction between the earth and the sun No force is required to keep the earth moving
0 25
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0
0
0
2
3
4
0 5
A stationary soccer ball is kicked and rolls away over the grass. What quantity does it have after the kick that it did not have before? 1. 2. 3. 4. 5.
Answer: 5 The momentum of an object is a equal to its mass times its velocity
p = mv
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0
0
0
2
3
4
0 5
A Radio Flyer wagon carrying one school book rolls along a level sidewalk. Which other Radio Flyer would have MORE momentum?
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D'Amato PTHS 2007
Momentum
Answer: 3
p = mv
1. A wagon loaded with school books, not moving 2. An empty wagon rolling at the same speed 3. An identical wagon rolling faster 4. None of these
Momentum increases when velocity increases or when mass increases
0 29
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Momentum
Mass Force Inertia Impulse Momentum
0 27
26
1 D'Amato PTHS 2007
0
0
2
3
0 4
30
D'Amato PTHS 2007
5
Cart A and cart B roll toward each other on a smooth track and collide. What quantity will always be the same before and after the collision? 1. The force of A plus the force of B 2. The speed of A plus the speed of B 3. The velocity of A plus the velocity of B 4. The total momentum of both carts 5. All these quantities stay the same 31
Answer: 4
pbefore = pafter mA vA1 + mB vB1 = mA vA 2 + mB vB2 Although velocities can change during a collision or explosion, the total amount of momentum remains the same
0
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0
0
0
2
3
4
0 32
5
What is the term we use when the total amount of some quantity remains the same before and after an event? 1. 2. 3. 4. 5. 6. 7.
Momentum
D'Amato PTHS 2007
Conservation
Answer: 5 If the total amount of some quantity remains the same, even though it can change form or be transferred, we say that it is conserved.
Coincidence Convergence Congruence Conditioning Conservation Constantiation Cromulence
In your personal finances, your net worth is conserved even though you may take money out of your bank account and put it in your pocket. This is always true after a visit to the ATM right?
$ wallet before + $ ATM before = $ wallet after + $ ATM after 0
33
0
1 D'Amato PTHS 2007
2
0
0
0
3
4
5
0
0
6
7
Chris throws a ball up in the air. If we say that the ball and the earth are the system, what does that mean?
34
System
D'Amato PTHS 2007
Answer: 3 system
1. 2. 3.
4.
The motion of the ball is determined by the earth The ball and earth obey rules of physics We are considering the ball and earth separately from Chris and other objects Nothing else interacts with the ball and the earth
The system is the part of the world we are interested in at the moment. It's a choice. The environment is everything outside the system. We draw the system with a circle around it. 0
35
environment
1 D'Amato PTHS 2007
0
0
2
3
0 4
36
D'Amato PTHS 2007
6
What do we call a force exerted by an object outside the system on an object inside the system? 1. 2. 3. 4. 5.
System
Answer: 4
Work Energy Interference External interaction Extrinsic force
ball and ramp: internal interaction
ramp and table: external interaction
An internal interaction is between objects in the system. An external interaction involves an object outside the system. 0 37
1 D'Amato PTHS 2007
0
0
0
2
3
4
0 5
Consider a system that includes a ball at the top of a ramp, the ramp, and the earth. What is an example of a process that could occur in this system? 1. The system is considered at an instant in time 2. The ball rolls to the bottom of the ramp 3. A hand holds the ball in place at the top of the ramp 4. The system is analyzed using physics rules 39
0
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0
0
2
3
Answer: 2 initial state
0 4
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Answer: 4 In any isolated system, mass never appears or disappears although it may change form. The same is true for energy and momentum.
initial state
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0
0
2
3
final state
Principles of conservation
Mass Energy Momentum Velocity
0 41
Energy
D'Amato PTHS 2007
A process is when the system changes from one state to another state over a period of time. The process is a change from an initial state to a final state
In any system of objects that does not interact with the environment, which of the following quantities is NOT always conserved? 1. 2. 3. 4.
38
final state
Bonus question: is this an isolated system?
0 4
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7
What is the real name of "Chalk smashing potential"?
Energy
Answer: 3 brick
1. 2. 3. 4. 5. 6.
Momentum Work Energy Temperature Inertia Height
earth
0
43
1 D'Amato PTHS 2007
0
0
0
0
2
3
4
5
We used the idea of "chalk smashing potential" as a way to visualize the concept of energy. A system can contain energy in many different forms. Energy is, technically, the ability to do stuff.
0 6
An object is raised above the surface of the earth. What kind of energy has been increased in the system of object and earth?
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D'Amato PTHS 2007
Gravitational Potential Energy
Answer: 4
Kinetic energy Vertical energy Potential energy Gravitational potential energy 5. Internal energy
brick
1. 2. 3. 4.
earth
0 45
1 D'Amato PTHS 2007
0
0
0
2
3
4
When an object and the earth are separated against their mutual attraction they gain more ability to do stuff if released. For a system to contain gravitational potential energy, the earth must be included in the system.
0 5
A fast- moving racecar slows down on a level track. Which statement is correct about the system that includes racecar, track, and earth? 1. Gravitational potential energy has decreased 2. Kinetic energy has decreased 3. Kinetic energy has increased 4. Kinetic energy has not changed 5. More than one of these is true 47
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D'Amato PTHS 2007
Kinetic Energy
Answer: 3 The energy of a moving object is called kinetic energy. If the object moves faster its kinetic energy increases
0
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0
0
0
2
3
4
0 5
48
D'Amato PTHS 2007
8
What is the term for an external interaction that changes the total amount of energy in a system?
Work
Answer: 4 brick
1. 2. 3. 4. 5.
Non-conservative force Impulse External influence Work Environmental factor
positive work
brick
When something from outside the system causes the total energy in the system to change, this is work If the total energy in the system increases we say positive work has been done 0
49
1 D'Amato PTHS 2007
0
0
0
2
3
4
0 5
Which situation describes a transformation of energy from one form to another?
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Energy Type of energy in the system
A block is supported 2m above the ground by a wire 2. A block is supported 2m above the ground by a stretched spring 3. A ball rolls at constant speed across a level surface 4. A ball is released from rest at the top of a hill, and rolls down 5. More than one of these decsribes a transformation of energy
1.
51
0
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0
0
0
2
3
4
5
Answer: 4 Increases when:
Decreases when:
Gravitational Potential Energy
System object moves higher
System object moves lower
K
Kinetic Energy
System object moves faster
System object moves slower
Something elastic is stretched or compressed from its rest position
Us
Elastic Potential Energy
Object is stretched or compressed more
Object is stretched or compressed less
Electric charges are separated
Uq
Electrostatic Potential Energy
More charges are separated
Fewer charges are separated
Symbol
Name
Something is elevated above the earth
Ug
Something is moving
0
Which statement describes an observation about fire walking?
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Observation
Answer: 1
1.
Some people walk on burning hot coals without injury 2. Evaporating perspiration cools the soles of the feet 3. The soles of the feet are protected by a layer of ash 4. Mental concentration and spiritual powers protect the feet 5. Some people will believe anything you tell them
An observation is a report of what you can see or measure, without any attempt to explain. Think of a radio announcer at a ballgame or a crime scene investigator trying to describe accurately and neutrally what she sees.
0 53
earth
earth
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0
2
3
4
0 5
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9
Which is a possible explanation for why people can walk on burning coals without injury? 1. Some people have a power of mind over matter 2. Evaporating perspiration protects the feet 3. A layer of ash insulates the feet 4. The coals are not really hot 5. All but 4 55
Think of how you could explain the phenomenon using what you know. You may need to propose a new idea to explain what you see -- maybe even magic.
0
0
0
0
2
3
4
0 5
How would we investigate possible explanations for why some people can walk on burning hot coals without injury?
57
0
0
0
0
56
Testing
Answer: 4 Ideas are tested by trying to show they are false.
0
Idea: "This is a good used car for me to buy" Prediction: "If I turn the key, the car will start" Test: Turn the key
2
3
4
5
How could you test the idea that mental concentration protects the feet during a firewalk?
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Testing
Answer: 4
1.
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D'Amato PTHS 2007
Use the idea to make a prediction. If the prediction does not come true, the explanation is no good.
1 D'Amato PTHS 2007
Ask many experimental subjects to attempt a firewalk using mental concentration 2. Ask many experimental subjects to attempt other feats using mental concentration 3. Ask subjects to describe how mental concentration works 4. Ask many experimental subjects to attempt a firewalk without using mental concentration
Answer: 5 An explanation is an idea that could possibly account for what you have observed.
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1. Ask people how they are able to perform this feat 2. Look for evidence to confirm our ideas 3. Find out what the experts think 4. List all possible explanations and try to disprove each one 5. Observe similar odd feats like fire-breathing
Explanations
The only definite conclusion is disproof. If you can firewalk without mental concentration, mental concentration is not necessary to walk over hot coals Idea: "This is a good used car for me to buy" Car starts: idea may be correct Tires are good: idea may be correct Brakes work: idea may be correct Hole in the floor: idea is NOT CORRECT 0
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0
0
2
3
Keep testing until disproved or satisfied with maybe!
0 4
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10
Which observation is NOT explained by the idea that liquids and gases are composed of a large number of tiny particles in continuous random motion? 1. Alcohol gradually disappears from paper 2. A balloon full of air has a round shape 3. Open a bottle of perfume and soon you will smell it 4. Milk eventually mixes into coffee even without stirring 5. ALL of these can be so explained 61
Kinetic Molecular Theory of Matter
Answer: 5 Tiny molecules are in constant random motion. Alcohol molecules jump off the paper sooner or later Air molecules collide continuously with the walls of a balloon Perfume molecules move among air molecules, across the room to your nose Milk and coffee molecules jostle and intermingle like dancers in a crowded club
0
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0
0
0
2
3
4
0 5
Which statement is NOT true about an inflated balloon?
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Kinetic Molecular Theory of Matter
Answer: 1 1. Air molecules are packed together tightly inside 2. Air molecules are continually colliding with the inside walls of the balloon 3. Air molecules are continually colliding with the outside walls of the balloon 4. The area inside the balloon 0 is mostly empty space 1 635. ALL of these are true D'Amato PTHS 2007
Air and other gases at room temperature are mostly empty space. Molecules move at high speeds through empty space, colliding with all surfaces and sometimes with each other These collisions cause gases to exert pressure on all surfaces A large number of tiny collisions feels like a continuous force 0
0
0
2
3
4
0 5
Which will NOT occur when the temperature of a box of gas is increased, according to our model? 1. Gas molecules will move more quickly 2. Gas molecules will collide with the walls of the box more often 3. Gas molecules will collide harder with the walls of the box 4. The amount of empty space inside the box will decrease 5. The pressure inside the box will increase 65
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Fluids at rest
Answer: 4 An increase in temperature means an increase in the speed of the rapidly moving microscopic particles In gas, this means more and harder collisions with surfaces including the walls of the container In liquid, this means its more likely that liquid molecules will escape each other and become gas
0
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0
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11
Consider four similar containers of liquid. In which will you measure the greatest pressure at the bottom of the ruler? 1.
Fluids at rest
Answer: 5
2.
Pressure in a liquid or gas is exerted because of the force required to support the fluid above. The depth below the surface of the fluid is the only factor that influences the pressure at any point flask
bucket
3.
4.
5. All pressures are the same
cylinder
0
funnel
67
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0
0
0
2
3
4
0 5
Consider the point indicated in an open container of liquid. In which direction is the pressure greatest? 1. 2. 3. 4. 5.
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D'Amato PTHS 2007
Fluids at rest
Answer: 5 At any small point, pressure is the same in all directions.
Direction 1 Direction 2 Direction 3 Direction 4 All the same
We explain this by saying that microscopic particles are colliding from all directions.
1
3
4 0
2
69
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0
0
0
2
3
4
0 5
Compare the pressure exerted by the liquid on the submerged block X at point A and point B 1. 2. 3. 4.
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Fluids at rest
Answer: 2 Deeper in the fluid means more pressure.
A is greater than B B is greater than A A is equal to at B There is not enough information to compare
Pressure is the same in all directions at a given depth.
A X
B 71
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0
0
2
3
0 4
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12
If block X is sinking in the fluid, what is the direction of the force exerted on the block by the liquid? 1. 2. 3. 4.
Fluids at rest
Answer: 1 There is always an upward force exerted by the fluid on a submerged or a partially submerged object
up down none There is not enough information to tell
But that does not mean the object will always float! Why not? Fliquid on block
block X
Does this block float or sink?
X
0 73
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0
0
2
3
0
Fearth on block 4
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13
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