Moments, Levers & Gears Practice Questions

Write down the equation which links distance ($d$), force ($F$) and moment of a force ($M$).

The mechanic applies a force of $45\ \text{N}$ to the spanner.

The perpendicular distance from the centre of the nut to the line of action of the force is $24\ \text{cm}$.

Calculate the moment of the force about the centre of the nut.

Moment of force = ______ N m

The nut does not turn.

Suggest how the mechanic could increase the moment about the nut without increasing the size of the force.

The student pushes the door with a force of $15\ \text{N}$.

The force acts at a perpendicular distance of $0.75\ \text{m}$ from the hinge.

Calculate the moment of the force about the hinge.

Moment of force = ______ N m

The student finds that a much bigger force is needed to open the door when she pushes close to the hinge.

Explain why.

Describe one other everyday example in which a force causes an object to rotate.

Explain why the weight of the metre rule does not need to be included in the student's calculations.

Calculate the anticlockwise moment of the $2.0\ \text{N}$ weight about the pivot.

Moment = ______ N m

Determine the mark on the rule from which the $4.0\ \text{N}$ weight must be hung for the rule to balance.

Mark = ______ cm

Gear A is turned clockwise.

State the direction in which gear B rotates and explain why.

Gear B is larger than gear A.

Explain the effect this has on the speed of rotation and on the moment produced by gear B.

The teeth of gear A exert a force of $30\ \text{N}$ on gear B.

The radius of gear B is $0.09\ \text{m}$.

Calculate the moment produced about the axle of gear B.

Moment = ______ N m

Calculate the force the gardener must apply to the handles to just lift the load.

Force = ______ N

Explain how the wheelbarrow acts as a force multiplier.

The gardener moves the same load so that it is closer to the wheel.

Explain the effect this has on the force needed at the handles.

State where the weight of the plank acts and calculate the moment of the plank's weight about the pivot.

Moment = ______ N m

Determine the distance from the pivot at which the second child must sit.

Distance = ______ m

The second child then slides further along the plank towards end B.

Explain what happens to the plank.