Shock Absorbing

1. Nov 22, 2013

Miraj Kayastha

How does our body absorb the force from falling? And if we roll or bend our knees while landing why is the force felt by our body less?

Can somebody explain?

2. Nov 22, 2013

Pythagorean

In collision, the ground imparts force to you. The force is called impulse:

F = dp/dt
(where dp/dt is how your momentum, p, changes over time, t).

So if your momentum changes quickly over a short time, that's a bigger force than if it changes the same amount over a longer time.

If you bend your knees at the right rate, or you catch a ball by moving your hand in the direction the ball is going as you catch it, you are effectively lengthening the time over which the impulse is imparted, lowering the force.

Reducing impulse is involved in rolling too, but rolling is transforming your momentum into rotational energy so that you can slow yourself down throughout the roll (again reducing the time over which the impulse is imparted from the ground). Proper rolling technique also requires you unfold at the end of your roll, sprawling out your body to distribute the force over a larger area.

3. Nov 22, 2013

CWatters

If you don't bend your knees your whole body stops in a very short distance after the initial impact. If you allow your knees to bend the stopping distance for the rest of your body is increased.

If you have more distance over which to slow down the deceleration required is less. Newton law says Force = mass * acceleration. If the acceleration (or deceleration in this case) is smaller the force is smaller.