Question

We Can easily move our hand in air but to do the same through a solid block of wood we neednan karate expert. Why?

Answer 1

In air, there is lot of empty space between the molecules and the forces between the particles are almost negligible. Hence, we can move our hand in air. However we cannot move our hand in a solid block because there are strong forces of attractions between particles in a solid and there is no empty space between them.