- #1
Supernejihh
- 13
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Homework Statement
We must apply a force of magnitude 80N to hold the block stationary at x = -2.0cm. From that position, we then slowly move the block so that our force does +4.0J of work on the spring-block system; the block is then again stationary. What is the block's position? (Two answers.)
Homework Equations
F = -kx
W = (1/2)*k*xi^2 - (1/2)*k*xf^2
The Attempt at a Solution
80 = -k(-.02m)
k = 4000 N/m
With the spring constant, i plug it into the Work equation to find xf
4 = .5*4000*(-.02^2) - .5*4000*xf^2
3.2 = -2000xf^2
-.0016 = xf^2
And this is where I am stuck. The answer cannot be an imaginary number, but a real one. I know the equations are correct, so what am I doing wrong? Please explain.