Question

Friction is a/an
A) self-adjusting force
B) necessary evil
C) important force in daily life
D) all the above

Answer 1

Hint : Friction is the resistance to motion of one object moving relative to another. When two bodies are in contact with each other and any one body wants to move, they exert friction on each other.

Complete step by step answer
For any object to move, it must overcome the limiting friction between the two surfaces. When the force applied to a body is lower than the limiting friction, the friction force will rise along with the external force and the body won’t be able to move. If the applied external force is greater than the limiting friction, then the limiting friction will act on the body. Hence friction is a self-adjusting force so option (A) is correct.
Friction causes energy losses in machines and requires us to do more maintenance work and provide more energy for running machines. However, we would not be able to walk or drive cars on the road and many more such activities if friction didn’t exist hence friction is a necessary evil. So, option (B) is also correct.
Friction is what allows us to hold objects in day-to-day life, move around, pick something up, etc, so it is an important force in day-to-day life. So, option (C) is also correct.
Since all the options are correct, the correct choice is option (D).

Note
Friction always acts in the direction opposite to the direction in which the object is moving, or trying to move depending on the magnitude of the external force applied to it. We say friction is a necessary evil because it reduces the efficiency of machines however with the help of proper lubricants and designing, we can reduce the friction force very considerably.