Effect of roughness on frictional force:
1. Set up an inclined plane on the horizontal floor. Use a wooden board as inclined plane.
2. Put a mark at any point A on the inclined plane. Now let a pencil cell or ball move down from this point.
3. Note the distance covered by the pencil cell from the bottom of the inclined plane to point where it comes to stop.
4. Now, spread a cloth over the floor make sure that there are no wrinkles in the cloth.
5. Try again with pencil cell. Now note down the distance.
6. Distance covered by pencil cell is less in this case.
7. Thus we conclude that smoothness/ roughness of the surfaces of both the floor and the pencil cell could affect the distance travelled by it.
