A 3.00-m long plank of negligible mass has a 30.0-kg mass at one end and a 40.0-kg mass at the other end. How far from the 30.0-kg mass should a fulcrum be placed so that the plank is balanced?
A)1.71 m
B)1.29 m
C)0.750 m
D)1.50 m
E)2.25 m

Question

Quizplus · Accepted Answer

The torque due to the 30.0-kg mass is 30.0 kg * 9.8 m/s^2 * 3.00 m = 882 N*m. The torque due to the 40.0-kg mass is 40.0 kg * 9.8 m/s^2 * x = 392 N*m, where x is the distance from the 30.0-kg mass to the fulcrum. For the plank to be balanced, the torques must be equal, so 882 N*m = 392 N*m and x = 2.25 m.

A 300-M Long Plank of Negligible Mass Has a 30