What is elastic energy determined by.

The ability to get energy out depends on the material's elasticity. The energy stored in a spring depends on the: Distance the spring is deformed (stretched or compressed) The spring constant, which defines the amount of force required to deform a spring by a certain length (the work done on the spring).

the motion of a pendulum is a classic example of mechanical energy conservation. a pendulum consists of a mass (known as a bob ) attached by a string to a pivot point. as the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.