1. The problem statement, all variables and given/known data In the following figure, the boy has a mass of 40kg, and the platform he is sitting on has a mass of 15kg. If the force of the board on the boy is 180N; a) Find the acceleration of the boy b) Find the reading of the scale. http://www.csupomona.edu/~jarmand/131/131chall5s12_files/image002.gif [Broken] 2. Relevant equations F = ma 3. The attempt at a solution I think I have the acceleration kind of worked out with ƩFy = 2T - mg = may where m is the total mass of the system (platform + boy) and T is the tension in the rope. Would the force of the tension be the same as the reading on the scale? Mostly I've been unsure how to use that 180N. Then I started thinking that the downward force that the boy exerts on the chair has the same magnitude as the upward normal force that the chair exerts on the boy, giving ƩFy = T + Fn - mboyg = mboyay Two equations with two unknowns T and a: 2T -55(9.8) = 55a T + 180 - 40(9.8) = 40a ???