http://www.smartphysics.com/Content/Media/Images/Mechanics/06/acceleratingtruck.png [Broken] A box rests on top of a flat bed truck. The box has a mass of m = 24.0 kg. The coefficient of static friction between the box and truck is μs = 0.84 and the coefficient of kinetic friction between the box and truck is μk = 0.69. 3) What is the maximum acceleration the truck can have before the box begins to slide? The answer is 8.23 m/s^2 4) Now the acceleration of the truck remains at that value, and the box begins to slide. What is the acceleration of the box? The answer is 6.762 I did ukmg=ma but i don't understand why kinetic friction is the only force acting on the box.