GCSE Physics Moments and gears questions by topic

Complete the sentences about moments. (Physics only)

1. (a)Moment = force × perpendicular … from the pivot.[1]
2. (b)Moments are measured in …[1]
3. (c)For a balanced object, clockwise moments equal … moments.[1]
4. (d)Directly meshed gears rotate in … directions.[1]

A gate is pushed with a 20 N force acting 0.30 m from the hinge, at right angles to the gate. (Physics only)

1. (a)Write down the equation for the moment of a force.[1]
2. (b)Calculate the moment about the hinge.[2]

A see-saw balances with a 300 N child on one side and a 600 N child on the other. (Physics only)

1. (a)State which child must sit closer to the pivot.[1]
2. (b)Explain your answer using moments.[2]

A 15-tooth gear drives a 45-tooth gear. (Physics only)

1. (a)How does the driven gear’s speed compare with the driver’s?[1]
2. (b)State the direction of rotation of the driven gear compared with the driver.[1]
3. (c)State what has happened to the driven gear’s turning moment.[1]

A 600 N child sits 2.0 m from the pivot of a see-saw; an 800 N child sits on the other side. (Physics only)

1. (a)Calculate the moment of the 600 N child about the pivot.[2]
2. (b)Calculate how far from the pivot the 800 N child must sit to balance.[3]

A crowbar pivots 0.10 m from a 1 200 N load; the effort is applied 1.5 m from the pivot on the other side. (Physics only)

1. (a)Calculate the moment of the load about the pivot.[2]
2. (b)Calculate the effort needed to just lift the load.[2]
3. (c)Explain one trade-off the user accepts when using the crowbar.[2]

A student balances a uniform metre rule on a knife-edge at its 50 cm mark, then hangs a 2.0 N weight at the 20 cm mark. (Physics only)

1. (a)Explain why the rule balances at the 50 cm mark before any weights are added.[2]
2. (b)Calculate the moment of the 2.0 N weight about the pivot.[2]
3. (c)A second weight is hung at the 90 cm mark to restore balance. Calculate its weight.[2]

A 24-tooth driver gear turns at 60 rpm, transmitting a moment of 3.0 N m to a 72-tooth driven gear. (Physics only)

1. (a)Calculate the speed of the driven gear.[2]
2. (b)Calculate the moment delivered by the driven gear (assume no friction losses).[2]
3. (c)State the direction of the driven gear’s rotation.[1]

A uniform diving board is pivoted at one end. A 500 N downward force acts on the free end, 2.4 m from the pivot; an adjustable support is 0.60 m from the pivot on the same side. (Physics only)

1. (a)Calculate the moment of the 500 N force about the pivot.[2]
2. (b)Calculate the upward force the support must exert to hold the board steady.[3]
3. (c)Explain why the support force is much larger than 500 N.[2]

A bicycle has a 50-tooth chainwheel (front) and the rider’s pedals turn at 90 rpm. Two rear sprockets are available: 25 teeth and 10 teeth. (Physics only)

1. (a)For the 25-tooth sprocket, calculate the wheel’s rotation speed.[2]
2. (b)For the 10-tooth sprocket, calculate the wheel’s rotation speed.[2]
3. (c)Explain which sprocket the rider should choose to climb a steep hill, using moments.[3]
4. (d)Chain-linked gears turn the same way, unlike meshed gears. State why the chain matters here.[1]

A nut must be turned with a moment of at least 45 N m to loosen. A student can safely push with 150 N. (Physics only)

1. (a)Calculate the minimum spanner length (distance from nut to push point) needed.[3]
2. (b)The student can only find a 0.20 m spanner. Calculate the moment it delivers at 150 N.[2]
3. (c)Suggest and explain one way the student could still loosen the nut with the short spanner.[2]

A uniform 6.0 m beam of weight 900 N rests on a pivot 2.0 m from its left end. A crate sits on the left end of the beam. (Physics only)

1. (a)State the point where the beam’s weight acts.[1]
2. (b)Calculate the moment of the beam’s weight about the pivot, and state its direction of turning.[3]
3. (c)Calculate the crate weight needed at the left end to keep the beam balanced.[4]