Question

Alex (31kg) and Cassie (19Kg) sit on a 10kg metre-long see-saw at the local park. The pivot of the see-saw is in the middle of its length. If Cassie sits at one end of the see-saw, where relative to the other end must Alex sit so the net torque is balanced? (unit:metres)

Answer 1

Answer:

M1 g L1 = 19 kg * 9.8 m/s^2 * 5 m = counter clockwise torque - Cassie at left end

M1 g L1 = M2 g L2        for torques to balance

L2 = M1 L1 / M2 = 19 * 5 / 31 = 3.06 M

Alex should sit at 3.1 m from the fulcrum (at 5 m from each end)