Turning Effects of Forces

The diagram shows a stand. The stand holds a heavy mass above the bench.

Which two changes would definitely make the stand more stable?

• Lower the mass and make the base narrower.

• Lower the mass and make the base wider.

• Raise the mass and make the base narrower.

• Raise the mass and make the base wider.

A force of 4.0 N acts on a beam as shown.

The line of action of the force is a distance x from a pivot. The moment of this force about this pivot is 8.0 N cm.

What is distance x?

• 0.50 cm

• 2.0 cm

• 12 cm

• 32 cm

A uniform plank rests on a pivot at its centre. Two children P and Q sit on the plank in the positions shown.

The mass of child P is 25 kg. The plank is balanced. What is the mass of child Q?

• 20 kg

• 25 kg

• 31 kg

• 45 kg

A length of thread is attached to a lamina at point P, as shown in the diagram.

The lamina is free to rotate about point Q. The tension in the thread is F.

What is the moment of F about Q?

• Fw

• Fx

• Fy

• Fz

A student balances a non-uniform object on a pivot. To do this, a weight is suspended near the left-hand end of the object, as shown.

Where is the centre of mass of the object?

• A

• B

• C

• D