Friction opposes motion

– Case study and reasoning

Mr. Somu was driving his car at a high speed. Suddenly he saw a girl walking in front of him. He quickly stepped on the brakes and his car stopped about half-a-meter away from the girl.

How did the brakes help Mr. Somu’s car to stop?

The brakes increased the amount of friction between the car tyres and the roads.

Friction opposes motion so that it can cause a moving object to slow down and stop. The car stopped because all of  its kinetic energy was converted into other forms of energy while it worked against the extra friction produced by the brakes.

Would it have been a rainy day what would have happened?

There would be less friction between the car tyres and the road on a rainy day, so that the car would move a longer distance and knock down the girl before it  stopped.

Less friction is produced between surfaces that are wet or slippery.

Thus the car would move over a long distance before all its kinetic energy was converted to other forms of energy.

The car would eventually stop.

When objects are moving at the same speed, lighter objects possess less kinetic energy than the heavier ones.

The faster the object moves, the more kinetic energy it posses

Energy is required to exert a force.

Wind and running water posses kinetic energy and can do work.