Question

Why it becomes difficult to rub a black board after some time?

Answer 1

The chalk powder if left for a long time diffuses with the black board due to the process of diffussion and thus it becomes difficult for us to clean it

Answer 2

Answer:

Explanation:

(i) If the value of g becomes double,the force with

which the earth pulls the object i.e weight of

object becomes double.

(ii) As weightincreases,frictional force also increases

while pulling the object

( iii) Hence, it will become two times more difficult to

pull a heavy object along the floor.