AQA GCSE Science



Using the equation of moments of a force

Aims

Moments of a force have a turning effect on the objects to which the force is applied. In this exercise you will use the principle of moments to predict what will happen in different situations.

Questions

1. The picture below shows a boy standing in three different positions to balance a beam with a load on the other side of the pivot. The load is the same in each case and its distance from the pivot doesn’t change.

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a. In which position does the boy need to push down with the most force on the beam to keep it balanced? Tick your choice.

□ Position a

□ Position b

□ Position c

□ He applies the same force in each position.

b. In which position is the clockwise moment on the beam the largest? Tick your choice.

□ Position a

□ Position b

□ Position c

□ The moment is the same in each position.

□ The diagram shows a revolving door being used by three people, seen from above. The arrows show the force applied by each person inside the door.

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Work out the resultant moment about the pivot and state the direction of rotation of the door. (You can assume that the door is initially at rest and that any frictional forces can be ignored.)

2. The diagram shows a baby’s mobile. The dots on the arms of the mobile are 10 cm apart. Your task is to keep the mobile balanced by adding the weights shown to the empty boxes hanging off the mobile. You can use each weight only once. Remember that any suspension point of a balanced system carries the total weight of the masses hanging below it!

[pic]

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Name …………………………………………………… Class ………… Date ………………….

P3, Topic 2.1

Extension

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