AP Physics Forces Problem

Question

Two blocks of mass M and 2M, respectively, are directly next to each other left to right and are pushed along a smooth horizontal surface by a force F0.

Consider these two cases. In case A, the force F0 is exerted on the left side of the smaller block (mass M) and directed to the right. In case B, the force F0 is exerted on the right side of the larger block and directed to the left.

Is the acceleration of the blocks greater in case A or B, or the same? Explain your reasoning.

Also indicate whether the force of contact that block M exerts on block 2M is greater in case A, case B, or the same in both cases, and explain your reasoning.

Answer 1

a) acceleration of both blocks is the same in both cases as they are in contact and = F0/3M

b) the force of small block on large block is 2/3F0 in case A and the force of the large on the small is 1/3F0 in case B. Forces are different since acceleration is same for both blocks but masses are different.