A 1.25 kg weight is hung from a vertical spring. The spring stretches by 3.75 cm from its original, unstretched length. How much mass should you hang from the spring so it will stretch by 8.13 cm?
Remember Hookes law.
Hooke's Law relates Force a spring exerts to an object attached to it as:
where F is the force, k a spring constant, and x the distance it will stretch
So in your case, the spring constant evaluates to:
To get an 8.13cm extension you would need: