Question

Give reason for the following:
We can easily move our hand in air but to do the same through a solid block of wood we need a karate expert.

Answer 1

We can easily move our hand in air, but to do the same through a solid block of wood, we need a karate expert because the particles of air have large interparticle spaces and very weak interparticle force of attraction. Thus, one can easily move the hand in air and push the particles of air apart.

However, the particles of solid have very less interparticle spaces and have strongest interparticle forces of attraction.
Thus, a greater amount of force is required to move the particles of solid apart.