Question

A fulcrum is placed 1. 20 m from the edge of a 3. 70 m long wooden uniform plank that weighs 190 n. A weight fg is placed at the edge of the short end to balance it. How large must this weight fg be in order to balance the plank? (hint: first draw the weight vectors each in the correct location)

Answer 1

Middle of plank = 3.70 / 2 = 1.85 from left end

Fulcrum placed at 1.20 from left end

Clockwise torque = (1.85 - 1.20) m * 190 N = 123.5 N-m

Counterclockwise torque = F * 1.20 m

F = 123.5 N-m / 1.20 m = 102.9 N

102.9 N at the left end will balance the plamk