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GCSE Questions on pressure, buoyancy, upthrust and fluids

Q5. The diagram below shows some jaws used by the fire service. The jaws are opened and closed by a hydraulic system.

(a) The force applied at the effort piston is transmitted throughout the hydraulic system.

State the property of the liquid in the hydraulic system that allows this to happen.

Hydraulic fluid is virtually incompressible

[1 mark]

(b) The pressure in the liquid in the hydraulic system in the jaws is 5.2 × 108 Pa.

The cross-sectional area of the load piston in the jaws is 4.1 × 10–4 m2

Calculate the force at the load piston. ( Give your answer to two significant figures).

Pressure = force/contact area

5.2 × 108 = F/4.1 × 10–4

F = 5.2 × 108 x 4.1 × 10–4

F = 213,200

F = 210,000 N

[3 marks]

(c) How does the maximum force that the tip of the jaws can apply compare to the maximum force the load piston can apply? Give a reason for your answer.

The force at the tips is less because the tips are further away from the pivot point than the piston is.

[2 marks]

(d) In the diagram above the moments of the forces on the jaws are in equilibrium.

Explain what is meant by the statement 'the moments of the forces on the jaws are in equilibrium'.

The moments are equal in magnitude (size) and the moments are opposite in directionthey therefore cancel the effect of each other out - the clockwise moments equal the anticlockwise moments.

[2 marks]

[8 Marks TOTAL]