what is the distance and enrgy?

Question

A massless spring has a spring constant of 100 N/m. It is suspended vertically. A mass of 350 g is connected to the spring.

a) How far does the spring stretch?

b) What potential energy is now stored in the spring?

Answer 1

(a)

It stretches so that the upward spring force balances the downward weight.

ky = mg ⇒

y = mg/k = (0.350 kg)(9.8 m/s²) / (100 N/m) = 0.0343 m

(b)

U(y) = (1/2)ky²

You know k, and you have the result for y from part (a). Now plug in the numbers and get U in joules.