Turning Effects of Forces revision

Which of the following states the Principle of Moments?

• When a body is balanced, the sum of anticlockwise forces is equal to the sum of clockwise forces about the same pivot.

• When a body is balanced, the sum of anticlockwise moments is equal to the sum of clockwise moments.

• When a body is balanced, the sum of anticlockwise moments is equal to the sum of clockwise moments about the same pivot.

• When a body is balanced, the sum of anticlockwise moments and forces is equal to the sum of clockwise moments and forces about the same pivot.

The diagram shows a 20 kg wheelbarrow being used to transport a 100 kg load.

The combined weight of the wheelbarrow and load acts at point A.

Taking g = 10 N/kg, what is the resultant moment on the wheelbarrow?

• 40 Nm anticlockwise

• 120 Nm clockwise

• 552 Nm clockwise

• 47 400 Nm anticlockwise

The diagram shows a 8-metre long uniform beam.

After a 200 N upwards force is exerted as indicated in the diagram, the beam is balanced.

What is the mass of the beam?

• 56 kg

• 76 kg

• 124 kg

• 760 kg

Bob wants to make sure that his plastic water bottle does not topple amidst the strong winds.

Which of the following is not a measure Bob should take to prevent his water bottle from flying away?

• Choosing a water bottle with a larger capacity.

• Choosing a water bottle with a wider base.

• Filling the water bottle with water.

• Placing his water bottle indoors

In each setup, the dot represents the centre of gravity of the object.

Which of the following setups will the weight exert an anticlockwise moment that causes the object to topple?

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