1. The problem statement, all variables and given/known data find the fk in terms of M,m,a 2. Relevant equations 3. The attempt at a solution So what I got in the end result after decomposing the forces on each object and then do a substitution is : fk = m(a+g) - Ma, where m is the mass of the hanging block and M is the mass of the object in the plane. Is this wrong?