Question

Which of the following describe a frictional force?

• A. Frictional force always oppose the motion of an object
• B. Frictional force is parallel to the surface in contact
• C. Frictional force always produces heat.
• D. Frictional force can be increased or reduced.

Answer 1

Answer: (B), (D)

The correct options are
B Frictional force is parallel to the surface in contact
D Frictional force can be increased or reduced.

A frictional force does not always opposes the motion of an object. It is acted parallel to the surface of contact. It can be increased or decreased by many ways like using lubricants, roughening of a surface etc., Frictional force need not always produce heat.