A box of mass 27 kg is in the bed of a truck on a hill that is inclined at an angle of 26.1° above the horizontal. The tailgate of the truck is open. The truck is currently accelerating up the hill with a magnitude of 1.67 m/s2. themagnitude of the friction force from the truck on the box in this situation is 161.1N.
If the coeffcient of static friction between the box and the truck is 0.78, then what is the maximum acceleration that the truck can have if the box is not to slip
component of weight perpendicular to truck bed = 27*9.81 * cos 26.1
so max friction force resisting motion = (27*9.81 * cos 26.1 ) mu
put that in place of m a in your previous problem.