- #1
shawli
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Homework Statement
A 0.500 kg mass resting on a frictionless surface is attached to a horizontal spring with a spring constant of 45 N/m. When you are not looking, your lab partner pulls the mass to oneside and then releases it. When it passes the equilibrium position, its speed is 3.375 m/s. How far from the equilibrium position did your lab partner pull the mass before releasing it?
Homework Equations
Ee = 0.5 * k * x^2
Ek = 0.5 * m * v^2
Energy is conserved within the system: Einitial = Efinal
The Attempt at a Solution
At the equilibrium position, only kinetic energy is present.
At the "unknown" position, there is elastic potential energy because the mass has strayed from the equilibrium ...but since we don't know if the mass has been pulled to the maximum distance, I'm not sure whether or not there is kinetic energy. I'm not going to include it in my calculation because otherwise I'll have two unknowns ("x" and "v2")
Ek = Ee
0.5*m*v^2 = 0.5 * k * x^2
x = SQRT [ (m*v^2) / k ]
x = SQRT [ (0.500*3.375^2) / 45) ]
x = 0.36m
The answer is actually 0.19 m. I think I probably set up my equation incorrectly. Could someone look it over please?