When a `1.0kg` mass hangs attached to a spring of length `50 cm,` the spring stretches by `2 cm.` The mass is pulled down until the length of the spring becomes `60 cm.` What is the amount of elastic energy stored in the spring in this condition. if `g = 10 m//s^(2).`

Options

A. 1.5 Joule
B. 2.0 Joule
C. 2.5 Joule
D. 3.0 Joule

Answer

C

Explanation

Force constant of a spring
`k=(F)/(x)=(mg)/(x)=(1xx10)/(2xx10^(-2))rArr k = 500 N//m`
Increment in the length `= 60-50=10 cm`
`U=(1)/(2)kx^(2)=(1)/(2)500(10xx10^(-2))^(2)=2.5 J`