Problem 1

A small object of mass

m

is held at rest a height

h

above the free top of a light vertical spring of stiffness

k

standing on a horizontal floor. It is released, falls vertically, and contacts the spring; neglect air resistance and all losses, take compression as positive, and let gravity be

g

. Let

x

denote the greatest compression. (a) Find

x

and check the limit

h=0

. (b) Find the object's velocity when the compression is

y

, where

0\le y\le x

. (c) Find the compression at which its speed is greatest and that maximum speed.

problems.proof.stepOf

problems.proof.prevStep problems.proof.nextStep

mg(h+x)=\frac12kx^2

problems.proof.analysis

From release to maximum compression the object descends a total distance $h+x$ . Its speed is zero at both endpoints, so the lost gravitational potential equals the stored spring energy.