Question

Explain why:a)a pencil will write on paper but not on glass b) the handles of motor cycle are covered with a rubber sheet with spikes c) the soles of our shoes wear out gradually d) tyres of car wear out gradually

Answer 1

Friction is the result of rubbing of the surfaces of two materials together. This rubbing results in chipping off of bits of the materials rubbing together.

a)a pencil writes on a piece of paper but not on glass:
Friction between the pencil graphite and the paper removes bits of the graphite which leaves a mark on the paper. Glass surface is smooth and hence friction is less and writing is not possible.
b) Handles of a bike has rubber with spikes:
-This increases the friction due to the increased roughness and gives the biker a better grip on the handles.
c)Soles of our shoes wear out gradually:
-Friction between the sole of our shoes and the ground, makes bits of the parts of the soles of shoes to be chipped of gradually. This process takes time and soon the  soles wear out.
d)Tyre of car wear out gradually:
This is also due to friction. Friction cause the treads of the tired to be chipped off by the rough road surface eventually wearing out.

Answer 2

Answer -

a)a pencil writes on a piece of paper but not on glass:

Friction between the pencil graphite and the paper removes bits of the graphite which leaves a mark on the paper. Glass surface is smooth and hence friction is less and writing is not possible.

b) Handles of a bike has rubber with spikes:

-This increases the friction due to the increased roughness and gives the biker a better grip on the handles.

c)Soles of our shoes wear out gradually:

-Friction between the sole of our shoes and the ground, makes bits of the parts of the soles of shoes to be chipped of gradually. This process takes time and soon the  soles wear out.

d)Tyre of car wear out gradually:

This is also due to friction. Friction cause the treads of the tired to be chipped off by the rough road surface eventually wearing out.