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## Homework Statement

A block moves along a frictionless surface with an initial velocity of 10 m/s. It contacts a spring of spring constant 350 N/m. Underneath the spring at and after the point of contact the ground is rough and applies a constant friction force of 45 N. The spring compresses 0.75 m before the mass stops. What is the mass of the block?

## Homework Equations

Ki + Ui = Kf + Uf

## The Attempt at a Solution

Ui and Kf are zero, so I had 1/2mv

^{2}= 45 + 1/2kx

^{2}, but I'm not sure where to put the friction force in the equation.

The answer is supposed to be 2.64 kg... Please help!