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## Homework Statement

A 2.4kg block is dropped onto a spring from hieght of 5m. When the block is momentarily at rest, the spring is compressed 25cm. Find the speed of the block when the compression of the spring is 15cm.

answer: 10m/s

## Homework Equations

[tex]K=\frac{1}{2}mv^2[/tex]

[tex]U_g=mgh[/tex]

[tex]

\Delta U = \Delta K

[/tex]

## The Attempt at a Solution

[tex]U_o=mgh=2.4kg(9.81m/s^2)(5m)=117.72J[/tex]

since all the potential energy gets converted into kinetic energy

[tex]117.72J=\frac{1}{2}mv^2[/tex] then I solve for v and plug the numbers in. I get the right answer but I know I'm doing it wrong because I'm not sure how to take the spring into acount, especially when the springs constant isn't given.