Newton's Second Law and Static Friction?

A crate of oranges weighing 149 N rests on a flatbed truck 2.0 m from the back of the truck. The coefficients of friction between the crate and the bed are µs = 0.28 and µk = 0.20. The truck drives on a straight, level highway at a constant 7.7 m/s.


(a) What is the force of friction acting on the crate? (N)





(b) If the truck speeds up with an acceleration of 1.0 m/s2, what is the force of the friction on the crate? (N)





c) What is the maximum acceleration the truck can have without the crate starting to slide? (m/s^2)

Newton's Second Law and Static Friction?
as simple as that





a) since the truck is moving with constant speed net horizontal acceleration Willl be 0m/s^2





so frictional force equals to zero Newton





b) now that truck has sped up by 1m/s^2


frictional force wil be coefficient of friction *mass * acceleration


mass = 149/9.8 ~ 15 kg





answer = 0.28*15 * 1 = 4.2 N





c) i don't know (why to misguide u?)