O-LevelPhysicsForces5054/22 · May/June 2020 · Q39 Marks

Fig. 3.1 shows part of a hydraulic press that is used to compress waste paper into a brick for burning. A force of 20 N is exerted downwards on the end of the handle. [Figure 3.1]

(a)(i)The force on the handle creates a moment about the pivot. Define the moment of a force.[2]
(a)(ii)Explain why the force exerted on piston P is greater than the force exerted on the handle.[1]
(b)Explain how the hydraulic press enables a greater force to be exerted on piston Q than is exerted on piston P.[2]
(c)(i)In moving the handle downwards, the 20N force moves through a distance of 0.60m and piston Q rises by 0.020 m. The force exerted by piston Q on the paper is 400 N. Calculate: the work done in moving the handle downwards[2]
(c)(ii)the efficiency of the hydraulic press.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

[C1] force x distance
[A1] force x perpendicular distance
[B1] smaller distance to pivot (than from P to pivot)
[B1] same / equal pressure on piston P and piston Q
[B1] larger area of piston Q (than piston P)
[C1] (W = Fd) numerical or algebraic
[A1] 12 J
[C1] (efficiency) = work output / work input numerical or algebraic, e.g. 400×0.02 / 12
[A1] 0.67 or 67%

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