Question

Why does an athlete take a longer jump if he comes running from a distance than when he jumps from the take off line

Answer 1

The athlete is not able to take a longer jump when he suddenly takes off from the line because he possesses "Inertia of Rest" because he takes the jump and since he tries to resist a change in the state of rest, he is not able to take a long jump.

However, when he runs from a distance and takes his time in doing that, then he already possesses "Inertia of Motion" and hence he does not resist any change in the state of motion when he takes his jump as he will still be in motion.

And that's how he is able to take a better or a longer jump. Hope you got the answer you needed.