Give examples showing that friction can be useful. What is the significance of friction in transport?

Without friction of rest, people and animals could not walk. Without friction, objects would slip out of their hands. Friction stops the car when braking. In winter, the road and sidewalks are sprinkled with sand in order to increase friction.
The friction force reduces the efficiency of the engines and other mechanisms of the car and railway trains, but without it, movement would have been impossible.

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