A 2.00-m long uniform beam of mass 4.00 kg rests on a fulcrum that is 1.20 m from one end when a 3.00-kg mass rests on that end and a 8.00-kg mass is placed at another location on the beam. How far from the end at which the 3.00-kg mass is placed is the location of the 8.00-kg mass?
A)1.45 m
B)1.75 m
C)1.35 m
D)1.55 m
E)1.65 m

Question

Quizplus · Accepted Answer

To balance the beam, the moments about the fulcrum must be equal. The moment due to the 3.00-kg mass is (3.00 kg)(9.8 m/s²)(1.20 m). The moment due to the 8.00-kg mass is (8.00 kg)(9.8 m/s²)(x), where x is the distance from the fulcrum. The beam's center of mass also contributes a moment: (4.00 kg)(9.8 m/s²)(0.30 m). Solving for x gives x = 0.55 m from the fulcrum, or 1.75 m from the 3.00-kg mass end.

A 200-M Long Uniform Beam of Mass 4