explain an activity to show that friction depends on the nature of two surfaces in contact .

Make an inclined plane on a smooth
floor, or on a table. You may use a
wooden board supported by bricks,
or books. [Fig. 12.4 (a)]. Put a mark
with a pen at any point A on the
inclined plane. Now let a pencil cell
move down from this point. How far
does it move on the table before
coming to rest? Note down the
distance. Now spread a piece of cloth

over the table. Make sure that there
are no wrinkles in the cloth. Try the
activity again

Repeat this activity by spreading
a thin layer of sand over the table.
Maintain the same slope
throughout the activity.