Suppose the monkey accelerates upward with acceleration ’a’ & the block, accelerate downward with acceleration a1. Let Force exerted by monkey is equal to ‘T’ From the free body diagram of monkey


The block & the monkey move in the same direction with equal acceleration. If initially they are rest (no force is exertied by monkey) no motion of monkey of block occurs as they have same weight (same mass). Their separation will not change as time passes.