Homework Help: Energy - Finding Spring Constant

1. Jan 21, 2012

njanek

1. The problem statement, all variables and given/known data
If a mass (.5 lb) is pushed down a ramp at a constant unknown force into a spring, compressing it 3 inches, what is the spring constant?

2. Relevant equations
Mass: .5lb
Time: 3 seconds
Length of ramp: 28 inches
inital height of ramp: 5.5 inches
final height: 0
µ: .52
The ramp angle is 15o to the ground

3. The attempt at a solution
I understand that if I set the equation up like this:

1/2mv2o + mgho + 1/2Kx2o + Wnc = 1/2mv2 + mgh + 1/2Kx2

And plug in what I know, I will find the answer for the spring constant, But I'm having trouble finding the work of the non conservative forces. and the final and initial velocities. I just need help figuring them out so I can solve for K.

Thank you to anyone who helps :) I really appreciate it!

2. Jan 21, 2012

Delphi51

If the unknown force is large, it will give the mass a lot of energy and the spring will have to be very strong. Or if the force is very small, the spring will be very weak.
The strength of the spring depends on the force and cannot be found without knowing the force. Or something else not given in the question.