Question

Which of the following describe a frictional force?

• A. Frictional force always opposes the state of 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: (A), (B), (C), (D)

The correct options are
A Frictional force always opposes the state of 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

A) Friction is a force that always opposes motion all motion it always acts in a direction exactly opposite to that in which it is moving and stops when the surface rubs or drags against another as it moves.

B) Like the normal force, it is caused by direct contact between surfaces. However while the normal force is always perpendicular to the surface the frictional force is always parallel to the surface in contact.

C) Frictional force produces heat due to increase in internal energy of the molecules which interact with each other and hence the electrons create a radiation which is heat energy.

D) Frictional force can be increased by increasing the normal force.Alternatively frictional force can also be decreased by applying lubricants.