Chris and Robin use a 3m, 40kg, plank to span 2m over a river. The plank is set up with 1.0m on the bank and Robin is standing so that her centre of mass is 0.2m from the end. The diagram attached shows Chris (50kg) walking out on the plank. Robin has a mass of 80kg.
How far can Chris safely walk from the bank?
t = Fd
The Attempt at a Solution
T(robin) = T(chris)
(50*9.80)r = (80*9.8)(2)
r = 3.2 m ??
I can't seem to see any other way of working the answer out? CAN someone please give me a push in the right direction?