Easy Energy Conservation. Spring, Incline/Ramp, Friction.

[mcleanrs]

Homework Statement

Question for search purposes:

A crate is placed against a compressed spring on an incline. When the spring is released, the crate moves up the ramp and comes to a stop.

How far was the spring compressed?

Hint: The mass and the spring may not be in contact at the end.

 

[cepheid]

Your equation for energy conservation looks okay. I would have formulated it as:

spring elastic potential energy lost = grav. potential energy gained + work done by friction

which is a slightly more intuitive ordering to me.

It looks like you forgot a factor of g in your expression for the normal force, which should of course end up having units of force, not mass.

 

[mcleanrs]

Thanks for your help. I agree that they were ordered funny -- but by the time I realized that, I was feeling too lazy to redo my diagram!

Anyway, I tweaked some things, and now my answer is even further off! I am being tested on this Monday, so I appreciate the help...got to figure these concepts out!

I just double and triple checked this for accuracy...I am getting exactly what my math is telling me I should get, so I must have set something up wrong or something.

Hold it -- duh. Hold it. Got my spring equation off a little.

 

[mcleanrs]

Solution

 

[cepheid]

Glad to see you sorted it out.

 

[mcleanrs]

Yeah, thanks for the help. It's hard to wander through the algebra forest looking for mistakes when you're not even sure your Physics is right ;)