A uniform beam with a mass of 120 kg and a length of 5.0 m rests on two supports, one at the left edge and one 3.0 m from the left edge. How close to the right edge can a 68-kg person walk along the beam without causing it to tip over?
A)1.6 m
B)1.8 m
C)0.88 m
D)1.5 m
E)0.50 m

Question

Quizplus · Accepted Answer

The beam will tip if the net torque about the left support is clockwise. The torque due to the person is counterclockwise, and the torque due to the beam's weight is clockwise. The person can walk as close to the right edge as possible without causing the beam to tip if the net torque is zero.$$\sum 	au =0$$$$-(68	ext{ kg})(9.8	ext{ m/s}^2)(x)+(120	ext{ kg})(9.8	ext{ m/s}^2)(2.0	ext{ m})=0$$$$x=1.6	ext{ m}$$

A Uniform Beam with a Mass of 120 Kg and a Length