CHAPTER 3 : FORCE AND PRESSURE

SPM 2003, Section A, No.5 [8 Marks]1 Figure 7, Figure 8 and Figure 9 show a spring balance supporting a metal block K in the

situations.

Figure 7 Figure 8 Figure 9

(a) Compare the readings of the spring balance in Figure 7 and Figure 8.

…………………………………………………………………………………………………….

. …………............................................................................................................................

[1 mark]

(b) Name three forces that act on K when it is partially or totally in water.

……………………………………………………………………………………………………..

.. ……………………………………………………………………………………………………[2 marks]

(c) State and explain the relationship between the forces in (b)

……………………………………………………………………………………………………...

……………………………………………………………………………………………………..

. ……………………………………………………………………………………………………..[2 marks]

(d) Name the principle involved in (c).

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

(e) (i) What will happen to the reading of the spring balance in Figure 9 if the water is replaced with salt solution ?

…………………………………………………………………………………………………...

[1 mark]

(ii) Give one reason for your answer.

…………………………………………………………………………………………………..

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

30

SPM 2005, Section A, No.5 [8 Marks]2 Figure 5.1 show a piece of paper hanging from a retort stand. When air flows from the

nozzle of an air pump, the changes its position as shown in Figure 5.2

Figure 5.1 Figure 5.2

(a) Compare the position of the paper in Figure 5.1 and Figure 5.2

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

(b) F is a force that causes the paper to change its position.In box X, on Figure 5.2, indicate and label the direction of F that acts on the paper.

[1 mark](c) Explain how F is produced.

…………………………………………………………………………………………………….

…………………………………………………………………………………………………….[2 marks]

(d) (i) Compared to the position of the paper in Figure 5.2, how does the position of the paper change when the air flows faster.

………………………………………………………………………………………………….

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

(ii)Give a reason for your answer in (d)(i)

………………………………………………………………………………………………….

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

(e) Name the principle that causes the observation in Figure 5.2

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

(f) Name one piece of apparatus in a school laboratory which uses the principle in (e)

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

31

SPM 2006, Section A, No.5 [8 Marks]3 Diagram 5.1 shows the situation of a sheet of paper before and when air is blown.

Diagram 5.2 shows the situation of the canopy before the lorry moves when the lorry moves high speed.

Diagram 5.1

Diagram 5.2(a) What is meant by speed ?

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

(b) Based on Diagram 5.1 and Diagram 5.2 (i) State two similarities for the situation in Diagram 5.1 and Diagram 5.2

1. …………………………………………………………………………………………......

2. ……………………………………………………………………………………………..[2 marks]

(ii) Compare the air pressure above and below the paper when air is blown.

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

(iii) Relate the speed of the air to the pressure of the air.

……..……………………………………………………………………………………………

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

(c) Name the principle involved in 5(b)(iii)

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

32

(d) Diagram 5.3 shows an instrument used to measure the speed of air.

Diagram 5.3

In Diagram 5.3, the levels of coloured water in the U-tube are the same before air flows.(i) Compare the speeds of air at P and Q.

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

(ii) Mark the water levels in the U-tube in Diagram 5.3 while air flows.[1 mark]

SPM 2007, Section A, No.2 [5 Marks] 4 Diagram 2 shows a water tank that supplies water to a block a flats. The water flows to each

unit if the flat due to water pressure.

Diagram 2

(a) What is meant by pressure ?

…………………………………………………………………………………………………

33

Water tank

P

Q

[ 1 mark](b) A water tank with a height of 3.0 m is fully filled with water.

Calculate the water pressure at the base of the water tank. [Density of water = 1 000 kg m-3]

[ 2 marks]

(c) Based on Diagram 2, compare the water pressure at P and at Q. Explain your answer.………………………………………………………………………………………………….

…………………………………………………………………………………………………. [ 2 marks]

SPM 2008, Section A, No.7 [10 Marks]5 Diagram 7.1 shows a hydraulic system. A force F is exerted on the small piston.

Diagram 7.1(a)(i) Name the principle involved in this hydraulic system

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

(ii) Compare the pressure at point P and at point Q. …………………………………………………………………………………………………….

[ 1 mark]

(b)Diagram 7.2 show a hydraulic jack in a car service centre.

34

Large

Oil

Small

Large Piston

Oil

Valve B

Diagram 7.2

A force of 50 N is exerted on the small piston when the handle is pushed down. The cross-sectional areas of the small piston and the large piston are 0.04 m2 and 0.8 m2 respectively.

(i) Calculate the pressure exerted on the oil in the hydraulic jack.

[ 2 marks](ii) Calculate the force that the oil exerted on the large piston.

[ 1 mark](c) Based on Diagram 7.2

(i) Explain how the handle is used to lift the load to its maximum height.

………………………………………………………………………………………………….

………………………………………………………………………………………………….

…………………………………………………………………………………………………. [ 2 marks]

(ii) Explain one modification to the large piston that enables the jack to lift a heavier load.

…………………………………………………………………………………………………

………………………………………………………………………………………………… [ 2 marks]

(iii) State how load is lowered without using the handle.

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

35