Question

Give examples to show that friction is both friend and foe.

Answer 1

Hint: In this question, the concept of the frictional force is used, that is some time force restricts the motion of an object due to which there will be energy loss while, some time it helps like it helps us in walking on the surface.

Complete step by step answer
As the definition of Friction suggests, Friction is resistance to motion of one object moving relative to another. This is not a fundamental force like electromagnetic or gravitational force. But scientists believe that it is the result of the EM (Electromagnetic) attraction between charged particles in two touching surfaces. For every general rule of friction, there are many exceptions. Example, while two rough surfaces (such as sandpaper) rubbing against each other may get more frictional force. Smoothly polished materials such as plates of glass, which have been carefully cleaned from all surface particles, may stick to each other very strongly.
Friction is very necessary in our day – to – day life. It is necessary evil acting both as a friend and a foe.
So according to the question,
Examples of friction as a friend are:
-Walking is an example of friendly friction. We are able to walk because of the frictional force acting between our feet and the ground.
-Writing in a paper serves as friendly friction. Here frictional force acts between the pen and the paper surface.
-Screws and Nails stick to wall surfaces because of frictional force that acts between the two.
-When we light a matchstick, it serves as friendly friction. In this case the frictional force acts between the match stick and the stick and side surface of the match box.
Now, Examples of friction as a foe are:
-Production of Heat and wastage of energy takes place due to friction.
-Many times, the soles of the shoes wear out due to frictional force between the shoe and the ground.
-Vehicles and machines may consume more fuel due to friction and may incur high maintenance cost.
-If a tire deflates, it becomes difficult to move the vehicle due to increase in frictional force between the tire and the surface of the road.

Note
As we know that, friction force generally acts in the opposite direction of the motion, that is it opposes the motion of an object. The friction force depends on the surface roughness and the point of contact of the surface that is for rolling objects there will be less friction as compared to the flat objects.