I'm confused on this problem, I have found the acceleration of the forces, but I'm stuck with the the question below. Thanks for your help! Problem: An inventive child named Chris wants to reach an apple in a tree without climbing the tree. Sitting in a chair connected to a rope that passes over a frictionless pulley, Chris pulls on the loose end of the rope with such a force that the spring scale reads 250 N. Chris's true weight is 320 N and the chair weights 160 N. How do you find the force Chris exerts on the chair? I found the accelerationg of the forces, .408m/s^2 First of all, I know that his weight(320N) is being pushed down onto the chair. The chair also pushes him back up with (20 N, .408m/s^2 acceleration) Do I need to count in gravity also?? The answer is 83.3 N approx and I know a combination of numbers that would allow me to get that answer: 340N / .408 m/s^2 x 10m/s^2 I guess that isn't right? because the result would be in mass?? Help please.