7.4 Exercise 32

A hockey puck of mass 0.17 kg is shot across a rough floor with the roughness different at different places, which can be described by a position-dependent coefficient of kinetic friction. For a puck moving along the x-axis, the coefficient of kinetic friction is the following function of x, where x is in m: $\mu \left(x\right) = 0.1 + 0.05 x .$ Find the work done by the kinetic frictional force on the hockey puck when it has moved (a) from $x = 0$ to $x = 2 \text{m}$, and (b) from $x = 2 \text{m}$ to $x = 4 \text{m}$.