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### Transcript of Force and Pressure

FORCE AND PRESSURE 1. Photographs A and B show a boy pressing a thumbtack and a coin into a desk with the same amount of force .

Photograph A

Photograph B

a) He found that it is easier to press the thumbtack compared to the coin. Explain ,why? .. .. b) State a conclusion based on your answer in (a). ... ( 2 marks) ... c) The area of the coin is 3.14 x 104

(1 mark )

m . Calculate the pressure exerted by the coin ,if the force applied by the boy is 5 N.

2

( 2 marks )

er d) Explain why a bulldozer uses broad tyres .. .. ( 2 marks)

2.

3 A block of density 133 kg m-3 and dimensions 2 m 2 m 3 m is placed on a soft bed as shown in Diagram 4 below. The soft bed is compressed.

Diagram 4 (a) Why is the soft bed compressed? ....[1 ....[1 mark] (b) Give a definition for the concept in your answer in ( ? (a) ....[1 mark] ....[1 (c) Calculate the (i) Weight of the block

[3 marks] (ii) Pressure acting on the soft bed

[2 marks]

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3.

Diagram 5.1 and Diagram 5.2 show two balloons A and B exerted with the same force . gram

Diagram 5.1 (a) What is meant by pressure ?

Diagram 5.2

... [ 1 mark ] . (b) Based on Diagram 5.1 and Diagram 5.2, (i) Which balloon will burst easily? [ 1 mark] (ii) Compare the pressure exerted to the balloon ... .. . [ 1 mark] (iii) Compare the surface area of finger and needle which in contact with the balloon. .. .. [ 1 mark] (iv) Relate the pressure exerted on the balloon with the surface area . [ 1 mark] (v) What happens to the pressure on the balloon if force exerted is increased? . [ 1 mark] . (c) State the physics concept involved . . [ 1 mark] (d) State one application of physics concept in 5 (c) in our daily life .. .. [ 1 mark]

4.

Diagram 2.1 shows two different containers filled with water. The water pressure at point P and point Q are the same.

Diagram 2.1 (a) What is the meaning of pressure? [1 mark] (b) State one factor that affect the water pressure at point P and Q. [1 mark]

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(c)

Calculate the water pressure at point P.

[Density of water = 1000 kgm ]

-3

[2 marks] (d) Diagram 2.2 shows the water spurt when a hole is made near the base of container B.

Diagram 2.2 Diagram 2.3 shows the water in container B is replaced by liquid X which has higher density than water. replaced

Diagram 2.3 Sketch the spurt of liquid X in Diagram 2.3. [1 mark] 5. Diagram 5.1shows a water jet spurts out from a hole in a tall vessel at a distance, d1. Diagram 5.2 shows an oil jet spurts out from a hole at the same depth in a tall vessel at a distance, d2.

(a) What is the meaning of density? . [1 mark]

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(b) Observe Diagram 5.1 and Diagram 5.2, compare (i) Density of water and oil. [1 mark] (ii) The distance d1 and d2. [1 mark] (iii) The pressure produced by the water jet and the oil jet. [1 mark] (c) Based on your answer in (b), state the relationship between the density and the pressure of liquid. .. [1 mark] (d) Diagram 5.3 shows the location of a house water tank.

Explain why the water tank should be located on top of the roof. .. [3 marks]

6.

Diagram 7.1 shows a concrete water tank filled with water.

Diagram 7.1 (a) State a factor that affects the water pressure in the tank. ....................................................................................................................................................... ............................................................................................................................. .............................................. [1 mark] (b) (i) Compare the water pressure at P and Q .................................................................................................................................................................................................... ............................................................................................................................. ............................................................ ..................................................................................................................................................................................... ..................................................................................................................................................................................... [1 mark] (ii) Calculate the water pressure at Q. (Density of water = 1000 kg m )-3

[2 marks]

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(c) Diagram 7.2 shows water flows from the concrete tank to the house water tank.

Diagram 7.2 (i) What is the factor that causes the water to flow from the concrete tank to the water tank in the house? ........................................................................................................................................................................................ [1 mark] ............................................................................................................................. ................................................... (ii) The flow of water from the concrete tank to the house will stop at level P. Explain why the supply stops? ................................................................................................................................................................. .................................................................................................................................................................................................... .................................................................................................................................................................................. ..................................................................................................................................................................................... [2 mark] (d) (i) Suggest two modifications that can be done to ensure the water flow continuously to the house water tank. ) .................................................................................................................................................... .................................................................................................................................................................................................... ............................................................................................................................................................................ ......................................................................................................................... [2 mark] ................................................................................................................ (ii) Draw a water tank that can withstand high water pressure . ater [1 mark]

7.

Diagram 5.1 and Diagram 5.2 show two identical thistle funnels that are covered with rubber sheets and is immersed in measuring cylinders filled with liquid P which density is 0.8 g cm . A manometer is connected to the thistle funnel using rubber tube. The depth, h1 and h2 are measured from the surface of the liquid P to the rubber sheet.-3

(a) State the function of manometer? [1 mark] (b) Observe Diagram 5.1 and Diagram 5.2, (i) Compare h1 and h2. . [1 mark] (ii) Compare the difference in height of the water level in the manometer. . [1 mark] (iii) Name the physical quantity that represents the difference in height of the water in manometer. .. [1 mark]

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(iv)

Relate the answer in (b)(i) and (b)(ii). .. [1 mark]

(v)

Relate the depth of the liquid and the physical quantity in (b)(iii). . [1 mark]

(c) Liquid P with density 0.8 g cm in Diagram 5.2 is then replaced by liquid Q with density 1.0 g cm . Predict what will happen to the difference in height of the water in manometer and give your reason. e . [2 marks]

-3

-3

8.

Diagram 3 shows a model of Bourdon Gauge which is constructed by a student to measure the gas pressure.

(a) What is the initial reading X in terms of atmospheric pressure? . [1 mark] (b) State the direction of the motion of the silicone tube and the movable pointer when the air is blow into the silicone tube. [2 marks] (c) The sensitivity of the model is low. Suggest 2 methods that can be used to improve the sensitivity of the model. [2 marks] (d) If the model is used to measure the pressure of the cooking gas in a cylinder and the reading obtained is 1.6 atmospheric pressure, find the pressure of the cooking gas in the cylinder. [1 ma mark]

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9.

Diagram 5.1 and Diagram 5.2 show two dams with different shapes.

DIAGRAM 5.1 (a) Based on Diagram 5.1 and Diagram 5.2 (i) Compare the dams in Diagram 5.1 and Diagram 5.2.

DIAGRAM 5.2

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