Bab 2

CHAPTER 2: FORCES AND MOTION 1

Diagram 1.1 shows the distance-time graph for the motion of a runner who is running along a straight line. ss/ /mm 25 20 15

B

C

5

10

10 5

A

0

DIAGRAM XX

t/s

t/s

DIAGRAM 1.1 (a) Based on Diagram 1.1, what is the distance travelled by the runner after 10 s? …...………..……………………………………………..…………………………….. [1 mark] (b) What physical quantity is given by the gradient of the graph in Diagram 1.1? …...………..……………………………………………..…………………………….. [1 mark] (c) Describe the motion of the runner, (i)

from A to B

(ii)

……...……………………………………..…………………………………….. [1 mark] from B to C

……...……………………………………..…………………………………….. [1 mark] 2. Diagram 5.1 and Diagram 5.2 show two eggs released from the same height and drop on to Surface A and Surface B respectively.

Egg Does not break

Surface A DIAGRAM 5.1 (a) What is meant by impulse?

Egg Breaks

Surface B DIAGRAM 5.2

.........…………………………………………………………………………………… [1 mark]

(b) With reference to Diagram 5.1 and Diagram 5.2; (i)

Compare the force on the eggs that strike Surface A and Surface B.

(ii)

.....................…………………………………………………………………….. [1 mark] Compare the time of impact of the eggs on Surface A and Surface B.

.....................…………………………………………………………………….. [1 mark] (iii) Compare the change in momentum of the eggs in both situations. .....................…………………………………………………………………….. [1 mark] (iv)

State the relationship between the force produced in a collision and the time of impact. .....................…………………………………………………………………….. [1 mark]

(v)

Suggest a suitable material for Surface A. .....................…………………………………………………………………….. [1 mark]

(c) Diagram 5.3 shows a pile hammer used in driving a pile into the ground at a construction site.

Pile hammer

Pile

DIAGRAM 5.3 / RAJAH 5.3 Explain how a large force is produced by the pile hammer in driving the pile into the ground. ……………..…………………………………………………………………………... ……………..…………………………………………………………………………... ……………..…………………………………………………………………………... [2 marks]

Diagram 2 3. Diagram 2 shows a boy jumping from a high position a) i) What will the boy do before reaching the floor? ……………………………………………………………………………( 1 mark ) ii) Give a reason for (a)(i). ………………………………………………………….……………….. ( 2 marks ) b) The mass of the boy is 60 kg . His velocity upon reaching the floor is 5 ms −1 and he stops in 0.3 s. Calculate the impulsive force exerted on the boy. ......................................................................................................................................... . ........................................................................................................................................ .......................................................................................................................................... ......................................................................................................................... (3 marks)

Diagram 3 4. A child and an adult each sits on similar swings as shown in Diagram 3. a)

If they are given a push, which one of them is more difficult i) to be moved? …………………………………………………………………….( 1 mark ) ii) to stop? ……………………………………………………………….……( 1 mark ) iii) Give reason to your answers in (a)(i) and (ii) ……………………………………………………………… ……( 1 mark )

b) i)The property in which a body resists change from its state of rest or motion is known as inertia. Based on your answer in (a) state the relationship between the inertia and mass. …………………………………………………………..……….… .( 1 mark ) ii) Why does a supertanker needs to stop its engine over a distance of about 3 k m before it can finallycome to a stop. …………………………………………….………………………….( 2 marks ) iii) Give one positive effect of inertia ……………………………………………….………………………..( 1 mark )

5. Diagram 3.1 shows a car driven by a kidnapper has overtook a police car at 2.00 p.m. The police car then followed the kidnapper’s car. Diagram 3.2 shows a velocity against time graph for both cars. Police car

Kidnapper’s car

DIAGRAM 3.1 Velocity / ms-1 25

Police car Kidnapper’s car

20

0 2.00 pm

2.01 pm

2.02pm

Time

DIAGRAM 3.2 Based on graph in Diagram 3.2, state the motion of the (i) kidnapper’s car ……………………………………………………………………...................... [ 1 mark ] (ii) police car ……………………………………………………………………...................... [ 1 mark ] (a) (i) What is the net force acting on the police car after 2.01 p.m? ............................................................................................................................ [ 1 mark ] (ii) Give a reason for your answer in 3(b)(i). Beri sebab bagi jawapan anda di 3(b)(i). ............................................................................................................................ [ 1 mark ]

(b) Sketch a displacement against time graph of the police car. Displacement/m

0 2.00 pm

2.01 pm

2.02pm

Time [ 2 marks ]

6. Diagram 5.1 shows the movement of the box from point P to point Q when it is pulled by a worker . The time for movement from the point P to the point Q is measured using by a stopwacth Diagram 5.2 shows the pointer of stopwatch when the box is at point P and at point Q respectively.

DIAGRAM 5.1

DIAGRAM 5.2 Diagram 5.3 shows the movement of the box from point P to point Q when it is pulled by two workers . The time for movement from the point P to the point Q is measured by using a stopwacth Diagram 5.4 shows the pointer of stopwatch when the box is at point P and at point Q respectively.

Box

DIAGRAM 5.3

(a)

(b)

DIAGRAM 5.4 Name one force which acting to the box. ………………………………………………………………………........ [ 1 mark] Observe Diagram 5.1 and Diagram 5.3 .Compare the force of the worker that exerted on the box. …………………………………………………………………………….... [1

mark ] (c)

mark ] (d)

(e )

Observe Diagram 5.2 and 5.4 Compare the time taken to move the box between point P and Q. …………………………………………………………………………… … [1 Based on the answer (c ) , compare the acceleration of the box. …………………………………………………………………………........ [ 1 mark ] (i) Based on answer 5 (b) and 5 (d), state the relationship between the force of the worker and acceleration of the box. ……………………………………………………………................ [1

mark ] ( ii )

State the law involved. …………………………………………………………………...… [1

mark ] (f) (i)

Based on Diagram 5.3 ,what happens to the acceleration of the box if the box of bigger mass is used ?

………………………………………………………………………........... [1 mark ] ( ii ) Give one reason for your answer in ( f )( i ). ………………………………………………………………… [ 1 mark ] 7. Diagram 8.1and Diagram 8.2 show a weightlifter is making trial to determine the suitable method to lift a load of mass 60 kg for longer time.

DIAGRAM 8.1

DIAGRAM 8.2

(a) What is meant by equilibrium state? ……………………………………………………………………………… [1 mark] (b).

What is the weight of the load? [2 marks]

(c) In the space below, draw the scale drawing of the triangle of forces to determine the value of T1. [Use the scale 1 cm : 10N] [3 marks]

(d) Calculate the tension T2 in Diagram 8.2

[2 marks]

(e) Based on the answer in (c ) and (d), state the suitable way to lift the load for a long time. Give one reason for your answer. .................................................................................................................................... .................................................................................................................................... [2 marks] (e) If the weightlifter let go the load, calculate the final velocity of the load before it touches the surface of the ground.

[2 marks] 8. Diagram 5.1 shows a clown throwing two basketballs of the same mass towards a wall. Ball A is hard while ball B is soft due to insufficient pressure. Diagram 5.2 shows the condition of the balls when they hit the wall. It was noticed that ball A is rebounded with a higher velocity than ball B.

A

A

DIAGRAM 5.1

B

B

(a)

What is meant by momentum?

DIAGRAM 5.2

……………………………………………………………………………… [1 mark] (b)

Observe Diagram 5.1 and 5.2. (i) Compare the shape of the basketballs before and after they collide with the wall. ………………………………………………………………………….. [1 mark] (ii)

Relate the changes in velocity of the basketball and its hardness, to explain the observations in b (i). …………………………………………………………………………. …………………………………………………………………………. [2 marks]

(a)

The mass of a basketball is 0.5 kg moving at 9 ms-1 strikes a wall. The ball rebounds at 6 ms-1. Determine the impulse on the ball.

[2 marks] (d) List two of the safety features that are installed in a car to reduce injuries in an event of an accident. ………………………………………………………………………………… ………………………………………………………………………………… [2 marks]

9 . Diagram 2.1 shows a car and a lorry which has different mass approaching a zebra crossing with same velocity 15 m s-1.

When the driver in the vehicles saw Siti walking across the zebra crossing, they applied the brake at the same time until the vehicles came to a complete stop. (a)

What is meant by mass ? ………………………………………………………………………………… ………… [1 mark ]

(b) stop?

(i)

Between the car and the lorry in Diagram 2.1, which first came to a complete ..……………………………………………………………………………………

… [1 mark ] (ii)

Give one reason for your answer in (b) (i). ..……………………………………………………………………………………

… [1 mark ] (c)

If the lorry had traveled a distance of 375 m before it came to a stop, calculate the deceleration when the brake was applied until it stop. [2 marks ]