## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

$\mu_k = 0.25$
Since the safe moves with a constant speed, the acceleration is zero. We can set up a force equation to find the coefficient of kinetic friction. Therefore; $\sum F = ma$ $385~N+350~N-F_f = 0$ $mg~\mu_k = 385~N+350~N$ $\mu_k = \frac{735~N}{(300~kg)(9.80~m/s^2)}$ $\mu_k = 0.25$