Turning effects of forces

Four table lamps are shown along with the position M of the centre of mass in each case. Which lamp is the most stable?

• A

• B

• C

• D

The diagram shows an object of weight W and an object of weight Z balanced on a uniform metre rule.

Which equation relating to W, Z, a and b is correct?

• W/a = Z/b

• W x Z = a x b

• W × a = Z × b

• W × (a + b) = Z

The diagrams show three uniform beams P, Q and R, each pivoted at its centre.

The two forces acting on each beam are also shown.

Which beams rotate clockwise?

• P and Q only

• P and R only

• Q and R only

• P, Q, and R

A uniform horizontal beam, pivoted at its right-hand end, is in equilibrium. A force of 60N acts vertically upwards on the beam as shown.

What is the weight of the beam?

• 36 N

• 40 N

• 90 N

• 100 N

A bicycle pedal is connected to a pivot by a metal bar, as shown.

The force on the pedal is 60 N downwards. What is the moment of this force about the pivot?

• 7.2 Nm

• 9.6 Nm

• 12 Nm

• 1200 Nm