Question

Question 1
Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play

(a) only if the objects are solid.
(b) only if one of the two objects is liquid.
(c) only if one of the two objects is gaseous.
(d) irrespective of whether the objects are solid, liquid or gaseous.

Answer 1

(d) irrespective of whether the objects are solid, liquid or gaseous.

Friction acts in all forms of matter i.e. solid, liquid and gases. All friction requires is contact between two surfaces whether it is solid-solid, solid-liquid, liquid-gas, liquid-liquid or gas-gas.