1. The problem statement, all variables and given/known data Why must a water skier moving with constant velocity lean backward? What determines how far back she must lean? Draw a free-body diagram for the water skier to justify your answers. 2. Relevant equations Equilibrium: Fnet=0 and Torquenet=0 rcenter of mass=(m1r1+m2r2+m3r3...)/(m1+m2+m3...) This chapter also discusses stress, strain, elasticity etc. but I don't think it's applicable to this problem. 3. The attempt at a solution In my free body diagram, the forces acting on the skier are air resistance and water resistance in the negative direction, and the tension in the rope she's holding in the positive direction. The net force will always be zero because the tension will match resistance. The torque needs to be kept at 0 so she doesn't flip. I think she leans back to keep the torque at 0, but I'm not sure why that would work.