Question

Why doleaves of a tree may get detached if we vigourously shake its branch?

Answer 1

When we shake the branch of a tree, the leaves on it want to maintain their inertia of rest, but when the branch moves,  the leaves do not maintain this inertia and fall down. This is so because of the inertia of rest (static inertia) which is the fundamental property possessed by a body to oppose any change in its state of rest. Or in other words, the body does not want to change its state of rest, but wants to continue its state of rest is called inertia of rest.