Question

A ball of mass m is dropped from a height h on a platform fixedat the top of a vertical spring

Answer 1

Eenrgy Conservation principle,

We would take the refernce at dropping point and let h be the height of the ball from the platform

Thus,

0 + mgh = 0.5*k*x^2 + 0

k = 2mgh/x^2 is the answer.