Question

The efficiency of a machine is reduced due to friction
a) True
b) False

Answer 1

Hint: Friction arises due to the irregularities of the surface. Even the smooth surfaces possess some coefficient of friction which opposes the motion of the body. Hence we will use an analogy to see whether the friction decreases the efficiency of the machines.

Complete step-by-step answer:

If we see the above diagram, the frictional force acts opposite to the direction of motion. Even a smooth surface has some irregularity and hence offers frictional force. Let us say in the above case we apply a force F, sufficient enough to overcome the force of friction f. Hence the force of friction i.e. F is $\mu N$ where N is the normal force and $\mu $ is the coefficient of static friction. $\mu $ in reality not equal to zero.
In machines the pistons which move slide through the cylinder in which they are kept. In the above statement we concluded that the coefficient of friction in real life is not equal to zero. Hence we always have to do some extra work to overcome this friction. The efficiency of a machine will be 100 percent if and only if all the energy supplied to it is utilized to do mechanical work. But one has to do some work to overcome the force of friction, therefore we can conclude that friction is one of the factors that reduces the efficiency.

Note:It is to be noted that not only the surfaces provide frictional force but air does as well. The frictional force is a contact force. The frictional force is called the foe but at the same time it is very much essential as the things wouldn’t have been stationary the way we see in the real world.