PDF chapter test TRY NOW
Tie a string around a brick. Pull the brick by a spring balance. You need to apply some force. Note down the reading on the spring balance when the brick just begins to move. It gives you a measure of the of force of friction between the surface of the brick and the floor.
A brick is being pulled by spring balance
Now wrap a piece of polythene around the brick and repeat the activity. Do you observe any difference in the readings of the spring balance in the above two cases? What might be the reason or this difference? Repeat this activity by wrapping a piece of jute bag around the brick. What do you observe?
b. In the second instance, the brick's surface becomes smoother when it is wrapped in .
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