Moments of Forces

This diagram shows a non-uniform beam of weight 120 N, pivoted at one end. The beam is kept in equilibrium by force F. What is the value of force F?

• 30 N

• 40 N

• 360 N

• 480 N

The diagram shows a uniform bridge, 4.0 m long and weighing 10 000 N.

The bridge is pivoted at one end. A force at the other end gradually increases until the bridge begins to lift.

What is the lifting force as the bridge starts to move upwards?

• 2 500 N

• 5 000 N

• 10 000 N

• 20 000 N

The diagram shows a wooden beam of weight 20 N. The centre of mass of the beam is labelled M. There is a pivot at one end of the beam. The beam is kept horizontal by an upward force, F.

What is the magnitude of F?

• 12 N

• 20 N

• 30 N

• 33 N

A driver’s foot presses with a steady force of 20 N on a pedal in a car as shown.

What is the force F pulling on the piston?

• 2.5 N

• 10 N

• 100 N

• 160 N

A horizontal pole is attached to the side of a building. There is a pivot P at the wall and a chain is connected from the end of the pole to a point higher up the wall.

There is a tension force F in the chain. What is the moment of the force F about the pivot P?

• F x d

• F x h

• F x l

• F x s