Moments, levers and gears

Compare — 4 marks

A mechanic uses two different tools to loosen a stubborn bolt on a car engine. Tool A is a standard spanner with a handle length of 0.25 m. Tool B is an adjustable wrench with a handle length of 0.15 m. Both tools are applied perpendicular to the bolt at the same point, and the mechanic applies the same force of 150 N to each tool.

(a) Calculate the moment produced by each tool when the force is applied. [2 marks]
(b) Compare the effectiveness of the two tools for loosening the bolt. Explain your answer in terms of moments. [2 marks]

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(a) Tool A: moment = force × perpendicular distance = 150 × 0.25 = 37.5 N·m (1 mark)
(a) Tool B: moment = force × perpendicular distance = 150 × 0.15 = 22.5 N·m (1 mark)
(b) Tool A is more effective because it produces a larger moment (37.5 N·m compared to 22.5 N·m) (1 mark)
(b) The longer handle length of Tool A (0.25 m) creates a greater perpendicular distance from the pivot (bolt), which increases the turning effect for the same applied force (1 mark)

Explain — 3 marks

A gardener uses a spade to dig up soil. The spade has a long handle and a flat blade. When digging, the gardener pushes down on the handle while the blade stays in the soil. The soil acts as a pivot point (fulcrum).

(a) Explain why pushing down on the handle of the spade makes it easier to lift the soil compared to trying to lift the soil with bare hands. [2 marks]
(b) State the name of the turning effect produced when the gardener pushes down on the spade handle. [1 mark]

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(a) The spade acts as a lever / has a long handle that increases the distance from the pivot
(a) A larger distance from the pivot produces a larger turning effect (moment) with the same force / allows a larger force to be applied to the soil
(b) Moment / turning effect

Describe — 2 marks

A mechanic uses a crowbar to remove a stuck wheel nut from a car. The crowbar is 0.60 m long and the mechanic applies a downward force of 150 N at the end of the bar. The pivot point (fulcrum) is positioned 0.10 m from the nut.

(a) Describe how the position of the fulcrum affects the mechanical advantage of the crowbar as a lever. [1 mark]
(b) Describe the relationship between the effort arm and the load arm in this scenario, and explain why this arrangement makes it easier to remove the nut. [1 mark]

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(a) Moving the fulcrum closer to the load (nut) increases the mechanical advantage / increases the force applied to the nut
(a) OR: A longer effort arm relative to the load arm produces greater mechanical advantage
(b) The effort arm (0.60 m minus 0.10 m = 0.50 m) is much longer than the load arm (0.10 m)
(b) This large ratio of effort arm to load arm means a small effort force produces a large force at the load, making it easier to remove the nut

Compare — 4 marks

Explain — 3 marks

Describe — 2 marks

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