# Horizontal spring with friction

## Homework Statement

A spring with negligible mass has a constant of 105 N/m. It has been compressed horizantally with a 2 kg mass for a distance of 0.1m. If the mass has moved after release for a distance of 0.25m, what is the coefficient of kinetic friction between mass and horizontal surface.

## Homework Equations

F=-kx (spring force)
f= C N, f is friction, C is the kinetic friction coefficient, and N is the force exerted on the mass by the horizontal surface

## The Attempt at a Solution

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i would recommend using work to solve this problem.
Work=force*distance
also work done by a spring is .5*k*x^2

Conservation of energy would be the easiest way to solve this.
What happens to the potential energy initially stored in the spring?

hello
ok the work done by the spring is 0.5*k*x02 - 0.5*k*x12
we know that x0=-0.1m
but what is x1, since the 0.25m given in the question is the distance not the displacement??!?

ok i see what you mean ap123
the energy stored initially = the work done by the friction force
0.5*k*x0^2= C * mg * distance

Yes, you've got it :)