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## Homework Statement

So, I have a 5.0 kg rat that goes down a ski slope, slides along a rough patch, and then smashes into a vertical board with a spring attached. I need to find out the efficiency of the spring with this information:

m=5.0 kg

v (after sliding across rough patch)=108 m/s ; it also says that because of internal friction, the velocity is 50% than above, so it's 54 m/s (after hitting the board and spring)

[tex]\Delta[/tex]x=2.42 m (the magnitude of the spring's compression)

## Homework Equations

e=e

_{out}/e

_{in}(100%)

Possibly E

_{k}=.5mv

^{2}and E

_{elastic}=.5k([tex]\Delta[/tex]x)

^{2}

## The Attempt at a Solution

Well, I think that E

_{in}is equal to E

_{k}, as this is the energy required for the spring to compress, but I'm not completely sure of E

^{out}. Is it possibly E

_{elastic}(I know this value from a previous question)? If I use these two though, I get an answer around 400%, which is obviously wrong.