form 2 chapter 7.doc

7/29/2019 Form 2 Chapter 7.doc

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Form 2 ScienceChapter 7

FORM 2 CHAPTER 7

DYNAMICS

1. (a) Name the forces shown in Diagram 1.1.

(b) Diagram 1.2 shows a girl playing hockey.

State two effects of force on the ball when the girl hits the ball with a hockey stick.

(i) .

(ii) .

2. A worker pushes a sack of rice using a trolley to the shop as shown in Diagram 2.1.

JPN Pahang 2009 106

Diagram 2.1

Diagram 1.2

(i) .. (ii) ..

(iii) .. (iv) ..

Diagram 1.1


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(a) If the frictional force between the trolley and the ground is 500 N, calculate the work doneby the worker.

(b) A boy tries to push the sack of rice but the sack is too heavy for him to move.

(i) Did the small boy do any work?

.

(ii) Why?

.

(c) The worker carries a sack of rice weighing 50 kg upstairs. If the mass of the man is 65kg, calculate the work done in Diagram2.2.(1 kg = 10 N)

(d) The worker takes 5 minutes to complete the work in (c). Calculate his power.

3. Diagram 3.1 shows a wooden block being pulled on a table top.

JPN Pahang 2009 107

Diagram 2.2

Wooden block

Smooth table top

Spring balance

Diagram 3.1


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(a) Name the forces acting on the wooden block.

(i)

(ii)

(b) Using, draw the direction of the frictional force acting on the wooden block in the boxprovided in Diagram 3.1.

(c) What will happen to the reading of the spring balance if the same wooden block is pulledalong a piece of sand paper?

(d) Diagram 3.2 shows a man pushing a box towards the wall.

(i) Suggest one way on how he can reduce the force needed to push the box.

..

(ii) If the force needed to push the box is 300 N. Calculate the work done by the man inpushing the box towards the wall.

4. Diagram 4.1 shows some methods used to reduce friction.

(a) Name method P, Q, and R on Diagram 4.1.

JPN Pahang 2009 108

Wall

Box

5 m

Diagram 3.2

P: .. Q: .. R: ..

Diagram 4.1


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(b) Diagram 4.2 shows some used tyres.

(i) What has happened to the surfaces of the tyres?

.

(ii) Explain your answer in (b)(i).

.

(c) Diagram 4.3 shows two persons walking.

(i) State one advantage of friction in this situation.

(ii) State one disadvantage of friction in this situation.

JPN Pahang 2009 109

Diagram 4.2

Diagram 4.3

form 2 chapter 7.doc

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