Question

A vertical spring with spring constant k=900N/m , is attached to a table and is compressed down by 0,155m. What upward speed can it give to a 0,39kg ball when released?

Answer 1

$$0.5mv^2=0.5kx^2\to 0.39v^2=(900)(0.155)^2$$

$$v=7.45\frac{m}{s}$$