A spring is compressed so as to add U units of potential energy to it. When this spring is instead stretched to one-half the distance it was compressed, its potential energy in the same units will be

1/4 of Ec

Explanation:

Given that a spring is compressed so as to add U units of potential energy to it. The elastic potential energy will be

Ec = 1/2Ke^2

When this spring is instead stretched to one-half the distance it was compressed, then new e = 1/2 e

Substitute e into the formula above.

Es = 1/2 × K × (1/2 × e)^2

Es = 1/2 × K × 1/4 × e^2

Or

Es = 1/4 × 1/2Ke^2

Substitute Ec into the Es above

Es = 1/4 of Ec

Therefore, its potential energy in the same units will be one - fourth of the potential energy when compressed.

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.