Question

Which of the following is true about friction?
(a) Friction is a force that occurs only between solids.
(b) Friction is a force that only occurs on rough surfaces.
(c) Friction is a force that only occurs when an object moves.
(d) Friction can only slow things down.

Answer 1

(a) Friction is a force that occurs only between solids. - False
It can occur between liquids, solids or gases.
(b) Friction is a force that only occurs on rough surfaces. - False
It occurs on smooth surfaces also, but is minimal on such surfaces.
(c) Friction is a force that only occurs when an object moves. - False
It can occur even when an object is at rest.
(d) Friction can only slow things down. - True