Friction Extra questions

(i)The maximum force that is required to move an object from other object’s surface is called limiting friction.
(ii)Friction between two bodies when one body is moving with a uniform velocity upon the other body is called dynamic friction. It includes sliding friction and rolling friction both.
(iii)A force of friction that is produced when an object slides upon the surface. So, the area of contact between the object and other surface produces friction, called sliding friction.
(iv)A force of friction produces when an object rolls over the surface of other is called rolling friction.
(v)A force of friction produces when the body moves through the fluid. The area of contact between the body and fluid produces friction, called fluid friction or drag.

According his experiment, he noticed that the wooden log is cylindrical in shape while the wooden box is a cube-shaped therefore, while rolling the wooden log, rolling friction applied and sliding the wooden box applied the static friction. As we know, friction decreases in the case rolling friction. Moreover, rolling friction is less than static friction. Thus, Raman rolls the wooden log easily whereas he applies a great amount of energy for pushing the wooden box.

The factors that effects the fluid friction are shape of the object, speed of the object and nature of the fluid.

Submarines have streamlined body to experience less amount of friction while moving through water.

We use ball bearings in the tyres because these ball bearings convert sliding friction into rolling friction which makes the movement easier.

We change rough surfaces into smooth surfaces by polishing them.

Weightlifters use powder before lifting the weight because it increases the friction and provides a firm grip while lifting the weight.

By rubbing the matchstick on its cover, friction produces the heat that lights up the head of the matchstick.

We walk on the road because friction helps us to provide a grip while walking on the grass less soil is difficult because there is no friction.

1. Take two 50 kg blocks of cylindrical and cube shapes. Mark two points in your courtyard A and B at distance of 100 m. Take a stopwatch and observe the time in both the cases.
   
2. First, try to slide the cube block from point A to point B.
   
3. Second, try to slide the cylindrical block from point A and point B.
   
4. You noticed that cube block took 10 minutes and required a great amount of energy to push it from point A and point B whereas, cylindrical block took only 2 minutes and less energy.
   
5. Thus, this experiment shows that rolling friction is less than sliding friction.