A spring loaded gun question from my test.

[Krislynn]

A spring loaded gun question from my test. Please Help!

Homework Statement

Suppose a .16kg mass on a spring loaded gun that has been compressed .10 m has elastic potential energy of .85 J. How high above the spring's equilibrium point can the gun fire the mass if the mass is fired straight into the air?

Homework Equations

I am not even sure which equations to use!

The Attempt at a Solution

 

[Delphi51]

Welcome to PF, Krislynn.
The question is about energy. You are given the energy stored in the spring, so you must look up the formula for that. The spring energy is converted to the kind of energy the mass has when it is at its maximum height. You will need the formula for that kind of energy, too. The energy is entirely converted from one form to another, so you just put an equal sign between the two energy formulas, put in the numbers you know and solve for the height.

 

[Krislynn]

Thank you so much!

 

[Delphi51]

Most welcome! I now see you didn't need the spring energy formula because the energy was given. Just E = mgh should solve it.

 

[davidj89]

or if you feel like doing it the really clunky and obtuse way (what I did for some reason), .85=(mv^2)/2 solve for v and then its a really easy kinematics problem