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1. A rectangular concrete block with a dimension 0.5 m x 0.6 m x 1.0 m has a mass of 500 kg. Calculate the (a) maximum pressure (b) minimum pressure exerted by

the concrete on the ground.

3.1

Define Pressure and state its formula

Pressure is defined as _______________________ Pressure = Force Area

A

FP

The SI unit : ________ = ___________, Pa

State relation-ship between pressure

and area.

The pressure of a given force __________ as the surface area decreases.

Solve problems involving pressure

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2. A student pressing a thumbtack into a piece of wood with a force of 20 N. The surface area of the head of the thumbtack is 1 cm2 and the cross-sectional area of the tip of the thumbtack is 0.01 cm2. Calculate: (a) the pressure exerted by the

student’s thumb on the head of the thumbtack

(b) the pressure of the tip of the

thumbtack on the wood. (c) What conclusion can be drawn

from your answers to (a) and (b)?

3. Amy and Mimi are identical twins each weighing 450 N. The twins standing on one leg while doing an aerobic routine in a field. By comparing the pressure exerted on the field by the twins, explain why Mimi’s shoes are more suitable for the occasion compared with Amy’s shoes.

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1. A sharp knife has a very _____ surface area on its cutting edge so that ______ pressure can be exerted to cut the meat.

2. The studs on a football boot have only a _______ area of contact with the ground. The pressure under the studs is ________ enough for them to sink into the ground, which gives extra _______.

3. Nails, needles and pins have very _______ ends with very small surface areas.

When a force is applied to the head of a nail, the _________ pressure will drive its sharp end into a piece of wood easily.

1. Skis have a _________ area to reduce the pressure on the snow so that they do not ______ in too far.

2. A tractor moving on soft ground has ______ tires to reduce the pressure on the ground so that they will not sink into the ground.

2. Wall foundations have a large

horizontal area to ________ pressure on the ground.

A wide shoulder pad of a heavy bag will _________ the pressure exerted on the shoulder of the person carrying the bag.

Application of High Pressure Increasing the pressure by reducing the area

Application of Low Pressure :Decreasing the pressure by increasing area

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4. As a shop assistant, you are asked to place some nails bought by a customer in a plastic bag. However, the plastic bag is very thin and the nails will likely poke through it. Suggest way to place the nails in the plastic bag so that the plastic bag will not be poked or torn by the nails. Explain your answer.

5. Figure (a) shows a boy sitting on a horizontal wooden bar. When he stands on the same horizontal bar as in Figure (b) it breaks. (a) State one physical quantity that (i) remains constant in both

figure (a) and figure (b). (ii) varies from figure (a) to figure

(b). (b) Explain why the bar does not

break in figure (a) but breaks in figure (b).

TUTORIAL 3.1 1. 1 Pa is equivalent to

A 1 N m2 B 1 m N-2 C 1 N m-2 D 1 m N2

2. Figure shows a wooden block on

a horizontal surface. The block will exert maximum pressure on a horizontal surface if it is resting on its face

A STUV B TWXU C WXYZ D UVXY

3. The diagram shows a block with the dimensions of 1 m x 2 m x 3 m. The weight of the block is 1000 N.

What is the maximum pressure that can be exerted by the block on the floor? (2005) A 100.0 N m- 2 B 166.7 N m -2 C 333.3 N m - 2 D 500.0 N m -2

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4. The mass of a boy is 60 kg. The pressure exerted by the boy on a floor is 2 x 10 4 Pa. What is the area of contact between the shoe’s base of the boy and the floor. A 1.2 x 10 –2 m-2 B 3.0 x 10-2 m-2 C 4.5 x 10-2 m-2 D 6.0 x 10-2 m-2 E 8.0 x 10-2 m-2

5. Which shoe would exert the least

pressure on the ground when worn by the same lady? (2004)

6. Diagram below shows four different shapes of shoe heels worn by the same lady.

Arrange the heels based on the pressure exerted on the ground, in ascending order. (2006) A. P, Q, R, S B. S, P, Q, R C. R, P, Q, S D. S, Q, P, R

7. Which of the following wooden rods exerts the highest pressure on the floor if each load and each wooden rod has the same mass respectively? (2007)

8. Diagram 6 shows a durian and a

coconut of the same mass placed in two identical plastic bags.

Why does the plastic bag containing the durian tear more easily? (2008) A. The surface area of the durian

that is in contact with the plastic bag is larger

B. The force exerted by the durian on the plastic bag is larger

C. The pressure exerted by the durian on the plastic bag is larger

D. The volume of the durian is larger

9. The following diagrams show four

different postures of an elephant performing a circus. Which posture exerts the maximum pressure on the floor? (2010)

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Structure question 1. SPM 2003 paper 2 A8 Figure(a) and Figure(b) show two ways in which a gardener moves a wheelbarrow on a muddy road.

Figure(a) Figure(b)

(a) On Figure(a) and Figure(b), indicate and label: (i) the direction of force F

exerted by the gardener on the handle of each wheelbarrow to make it move.

(ii) the direction of the vertical component Fy , of the force in (a)(i)

[2 m]

(b)(i) Based on the answers in (a)(i) and (a)(ii), which of the ways is more suitable on the muddy road? [1 mark]

………………………………………..

[1 m] (ii) Explain the reason for your

answer in (b)(i). ………………………………… ……………………………………

[2 m] (c) The wheel of the wheelbarrow

exerted pressure on the muddy road . The resultant force exerted by the wheel on the road surface is 500 N and the area of the wheel in contact with the road is 2 x 10-3 m2.

(i) What does the word pressure mean?

…………………………………… [1 m]

(ii) Calculate the pressure exerted on the surface of the muddy road.

[2 m]

(iii)State one modification that could be made to the wheelbarrow to reduce the pressure exerted on the road. Explain your answer.

……………………………………… ………………………………………

[2 m]

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