1. The problem statement, all variables and given/known data If a 4kg block is placed on top of a 5kg block which placed on a friction less plane and a force is applied on the lower 5kg block ,For what maximum value of force will the top block not slide ? μ=0.036 2. Relevant equations 3. The attempt at a solution The maximum static friction that the top block can experience is fmax=μ mg=12 N But the force acts on the lower block so what will be the force on the upper block that the friction will counter? It would be nice to get a free body diagram.