How Much Force Do Arms Exert During a Chin-up Acceleration Phase?

[ils4826]

It first states that a body below the arms is raised at approx. 30 cm in a time of 1 second. It then specifically states that a body of 770 N is raised this distance and that half the 1 second is spent accelerating and the other half is spet decelerating, uniformly in both cases. The question is "Find the force his arms must exert on him during the accelerating part of the chin-up."? Does anyone know how I'd go about setting up for this problem? I tried making a free body diagram and don't really know where to go from here. HELP!

 

[Doc Al]

Start by figuring out the acceleration using your knowledge of kinematics. (Hint: Use the distance and time to find the acceleration.)