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Time: 20 minutes

UNIVERSITY OF SOUTH AUSTRALIA School of Electrical & Information Engineering (Applied Physics) ENGINEERING PHYSICS QUIZ 2 [ week 9 ] Marks: 20 Name ..................................................................................... QUESTIONS ( 10 MARKS )

ANSWERS

1. If the velocity of an object with a fixed mass is doubled then… A. Acceleration is doubled B. Potential Energy is doubled

C. Kinetic Energy is doubled D. Work is doubled

2. An object weighing 200 N hangs motionless from a string attached to the ceiling. The net force acting on the object is … A. 0 N B. 20 N

C. 200 N D. 2000 N

3. The weight of 600g of chocolate is? A. 0.588 N B. 5.88 N

C. 0.98 N D. 5880 N

4. A baseball player throws a ball vertically upward and catches it in the same spot when it returns to his mitt. At what point in the ball’s path does it have maximum kinetic energy? A. Midway on the way up. C. At the top of its trajectory. B. The instant it leaves the catcher’s hand. D. The instant before it arrives in the catcher’s mitt.

5.

A 2.00kg bag of onions is held for 50.0s at 1.00m above the floor. What is the work done? A. 0 J C. 19.6 J B. 10.2 J D. 980 J

6. Two identical vertical ropes support a stationary weight w. What is the tension in each rope (assuming the weight of the ropes is negligible)? A. w/2 B. 2w

C. w D. 9.8w

7. Which of the following is incorrect? A. B. C. D.

A force is conservative if the work done is path independent The potential energy is only defined for a conservative force Gravity is a non-conservative force Friction is a non-conservative force

8. A pilot flies in a vertical circle at constant speed. Which statement is true? A. The centripetal force at the top is greater than that at the bottom. B. The normal force is larger at the bottom than the top. C. The pilot would experience apparent weightlessness at the top. The mass of the pilot changes.

9. Terminal speed of a skydiver does not depend on A. The height they fell from B. Their mass

C.

Their surface area D. The density of the air

10. An object is given a push and it moves along a horizontal surface. What is the effect of the force of friction as the object moves? A. It does positive work on the object. B. It increases the object’s kinetic energy. C. It increases the object’s potential energy. D. None of the above.

QUESTIONS & PROBLEMS ( 12 MARKS ) Question 1 (4 marks) A toy plane tied to a string flies in a horizontal circle. Discuss all the forces acting on the plane. A diagram is essential. …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………… Problem 1 (4 marks) A child slides (from rest) down a slippery water slide (frictionless) into a pool below. If the slide is 4.00m in height, what is the speed of the child when he/she exits the slide at the bottom? (HINT use conservation of energy). ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… Problem 2 (4 marks) A satellite orbits 1500km above the surface of the Earth. Find the speed of the satellite and its period of orbit. (Mass of the Earth = 5.98x1024kg, radius of the earth = 6.37x106m, G = 6.67x10-11Nm2/kg2). ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………