1. 1
   A mechanic uses a long-handled wrench to loosen a stubborn wheel nut on a car. The wrench pivots about the centre of the nut, and the mechanic applies force perpendicular to the handle at a set distance from the nut.

   (a)

   What is the turning effect produced by the mechanic's force on the nut called?

   [1 mark]

   • AA moment
   • BA momentum
   • CA resultant force
   • DAn impulse

   (b)

   The mechanic finds the nut easier to loosen when using a longer wrench handle rather than a shorter one, applying the same force each time. Why does the longer handle make it easier to loosen the nut?

   [1 mark]

   • AA longer handle changes the force applied into a non-contact force
   • BA longer handle reduces the force needed because it makes the wrench lighter
   • CA longer handle increases the friction between the wrench and the nut
   • DIncreasing the perpendicular distance from the pivot increases the moment for the same applied force

   (c)

   The mechanic applies a force of 150 N perpendicular to the wrench handle, at a distance of 0.3 m from the centre of the nut. Calculate the moment produced.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Two children sit on a playground see-saw, which pivots at its centre. A lighter child sits further from the pivot on one side, while a heavier child sits closer to the pivot on the other side, and the see-saw balances perfectly level.

   (a)

   For the see-saw to balance perfectly, with total clockwise moment equal to total anticlockwise moment, what must be true about the two children's weights and distances from the pivot?

   [1 mark]

   • ABoth children must sit at exactly the same distance from the pivot
   • BBoth children must have exactly the same weight
   • CThe product of weight and distance from the pivot must be equal for both children
   • DThe total weight of both children combined must equal zero

   (b)

   The heavier child on the see-saw exerts a downward force (weight) at their seat. Which equation correctly relates the moment produced by this force to the child's weight and their perpendicular distance from the pivot?

   [1 mark]

   • AMoment = force divided by perpendicular distance from the pivot
   • BMoment = force x perpendicular distance from the pivot
   • CMoment = force x perpendicular distance squared
   • DMoment = force plus perpendicular distance from the pivot

   (c)

   The lighter child weighs 300 N and sits 1.8 m from the pivot. The heavier child sits 1.2 m from the pivot on the opposite side, and the see-saw is perfectly balanced. Calculate the weight of the heavier child.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A bicycle uses a system of two gears of different sizes connected by a chain to transmit the rotational effect of the rider's pedalling force to the rear wheel. A crowbar is also used nearby as a simple lever to prise open a heavy wooden crate lid.

   (a)

   Explain, using the idea of moments, how a gear system can be used to transmit the rotational effect of a force from one gear to another.

   [3 marks]

   (b)

   A crowbar is used as a simple lever to prise open a heavy wooden crate lid, with the pivot placed close to the lid and the person applying force at the far end of the crowbar, much further from the pivot. Explain how the crowbar allows the person to prise open the lid using a smaller force than would otherwise be needed, and describe the role of the perpendicular distance from the pivot in this explanation.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An engineer is designing a manually operated water pump for a rural village, which uses a long handle acting as a lever to make it easier for a single person to lift water from a well. The engineer also considers adding a small gear system to the pump's crank handle, to further adjust the rotational effect delivered to the pumping mechanism.

   (a)

   Explain the principle of moments and discuss how the engineer could use this principle to design a handle that minimises the force needed to operate the pump.

   [6 marks]

   (b)

   The engineer also considers adding a small gear system to the pump's crank handle, to further adjust the rotational effect delivered to the pumping mechanism. Discuss how a gear system, alongside the lever principle already used in the handle, could be used to further adjust the force or speed needed to operate the pump, and evaluate the trade-offs the engineer would need to consider.

   [6 marks]

   Total for question 4: 12 marks

End of questions