Principles of Moments

What is the anticlockwise moment acting on this crane?

• 20,000Nm

• 100,000Nm

• 120,000Nm

• 500,000Nm

What is the moment produced by a 15-Newton hanged cube?

• 1.5Nm (anticlockwise)

• 1.5Nm (clockwise)

• 150Nm (anticlockwise)

• 150Nm (clockwise)

The diagram shows a beam. Without any weights, the beam balances at its center.

Three weights are hang as shown.

At which point does a load of 2 N balance the beam?

• A

• B

• C

• D

A seesaw is unbalanced with two people of different masses sitting equal distances from the center. Which of the following will result in equilibrium?

• The larger person moving further away from the center.

• Moving the smaller person closer to the center.

• Moving the larger person closer to the center.

• Moving the two people away from the center

A boy of weight 600N sits on the see-saw as shown at a distance of 1.5m from the pivot. What is the force F required at the other end to balance the see-saw?

• 4.5Nm

• 100Nm

• 450Nm

• 600Nm

What is the anticlockwise moment acting on the seesaw?

• 1.6Nm

• 4Nm

• 10Nm

• 16Nm

State the principle of moments

• When a system is in equilibrium, the sum of the total clockwise moment is less than the sum of the total anti-clockwise moment about the same pivot.

• When a system is in equilibrium, the sum of the total clockwise moment is equal to the sum of the total anti-clockwise moment about the same pivot.

• When a system is in equilibrium, the sum of the total clockwise moment is equal to the sum of the total anti-clockwise moment about the different pivot.

• When a system is in equilibrium, the sum of the total clockwise moment is greater the sum of the total anti-clockwise moment about the same pivot.

The figure below shows a man lifting a heavy rock using a steel bar. He pushes downwards on the end of the bar with a force (F).

Which pivot positions allows the force (F) to be as small as possible?

• A

• B

• C

• D

Two bars, 10N and 6N were hanged from massless strings at the end of a light rod. If the 6-Newton bar is 4 m away from the pivot, how far should the 10-Newton bar be placed?

• 1.4 m

• 2.4 m

• 6.6 m

• 14.2 m

Two equal and oppositely directed forces acting on an object will be in equilibrium

• Only if they act on the same point on the object

• When they are balanced by a third force

• If they are separated by a distance

• when their moments about the same point are equal