## College Physics (4th Edition)

(a) The force of friction acting on the crate is zero. (b) The force of friction acting on the crate is $18.4~N$ (c) The maximum acceleration that the truck can have without the crate starting to slide is $2.94~m/s^2$
(a) Since the speed is constant, the net force on the crate must be zero. Therefore, the friction force acting on the crate is zero. (b) We can find the mass of the crate: $mg = 180~N$ $m = \frac{180~N}{9.80~m/s^2}$ $m = 18.4~kg$ We can find the force of static friction acting on the crate: $F_f = ma = (18.4~kg)(1.0~m/s^2) = 18.4~N$ The force of friction acting on the crate is $18.4~N$ (c) We can find the maximum acceleration that the force of static friction can provide for the crate: $F_N~\mu_s = ma$ $mg~\mu_s = ma$ $a = g~\mu_s$ $a = (9.80~m/s^2)(0.30)$ $a = 2.94~m/s^2$ The maximum acceleration that the truck can have without the crate starting to slide is $2.94~m/s^2$