Forces in action
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15. Useful and harmful effect of friction

Friction can be a useful force because:
Figure 9.10


- it prevents our shoes slipping on the pavement when we walk

- stops car tyres skidding on the road.

When you walk, friction is caused between the tread on shoes and the ground. This friction acts to grip the ground and prevent sliding.

Friction is not so useful everywhere. In some cases, friction is not required to execute the action.

- If you want to save energy and increase the efficiency of the engine, friction is not useful.

- When a spacecraft returns to the earth, it is highly affected by atmospheric friction. It requires much force, and energy is lost in the form of heat. The spacecraft must be fitted with a heat shield to bear this heat.

A

L

C