Activity 6.1 Let us investigate to see the difference in force of friction of different surfaces. Class 9

Activity 6.1 Let us investigate to see the difference in force of friction of different surfaces. Class 9

Activity 6.1 Let us investigate

Aim: To see the difference in force of friction of different surfaces.

Procedure: Take four coins kept on top of each other secured together with an adhesive tape and keep them on horizontal surface of wooden table top and on cemented floor. Place them near the middle of stretched rubber band. Push back stack of coins till the stretched rubber band is pulled back. Then release the stack of coins and observe its motion on two different surfaces of table top and cemented floor.

Observations and Conclusion: Before the stack of coins is released, it is stationary. When they are released, force applied by stretched rubber band in forward direction moves them. This shows that force applied by rubber band is larger than the force of friction, and net force acts on coins in forward direction. Thus velocity of coins increases and net force provides acceleration in the forward direction.

When coins lose contact with rubber band, force due to rubber band stops acting on it but force of friction continues to act upon them in opposite direction of their motion. It decreases velocity and brings them to rest.

Rubber band is stretched by same amount in each case but the distance travelled by coins on different surface changes. This tells that force of friction is different for different surfaces.