A 4.85-kg block is placed on top of a 12.0-kg block that rests on a frictionless table. The coefficient of static friction between the two blocks is 0.645. What is the maximum horizontal force that can be applied before the 4.85-kg block begins to slip relative to the 12.0-kg block, if the force is applied to the more massive block?

1 answer

force friction between blocks: 4.85*9.8*.645

The max acceleration: frictionforce/mass=9.8*.645 m/s^2

max horizontal force= (12+4.85)a