Question

A long elastic spring is stretched by `2 cm` and its potential energy is `U`. If the spring is stretched by `10 cm`, the `PE`…… will be
A. `5U`
B. `25U`
C. `U//5`
D. `U//20`

Answer 1

Correct Answer - B
The elastic potential is
Energy `=1/2"Stress"xx"Strain"`
`=1/2Y("strain")^(2)=1/2Y((/_l)/L)^(2)`
`:. (U_(2))/(U_(1)) prop((/_l_(2))/(/_l_(2)))^(2)=(10/2)^(2)`
`(U_(2))/(U_(1))=25impliesu_(2)=25U_(1)`