Question

Explain why, we can easily move our hand in air but to do the same thorugh a plank of wood, we need a karate expert

Answer 1

in air the relative distance between two particles is large where as in a wooden plank particles are closely packed
this offers higher resistance hence we need karate expert
it is same as walking on a empty road which depicts air example and walking on a road full of people which depicts plank example

Answer 2

Hey Friend here is your answer,

The molecules in air are very far from each other. They have enough space for interference of our hand.
Whereas a plank of wood is solid. The solid molecules are closely packed not allowing interference of our hand. Therefore Making us difficult to do the same In wooden plank.

HOPE YOU FIND IT USEFUL!!