Question

A rock of mass 170 kg needs to be lifted off the ground. One end of a metal bar is slipped under the rock, and a fulcrum is set up under the bar at a point that is 0.65 m from the rock. A worker pushes down (perpendicular) on the other end of the bar, which is 1.9 m away from the fulcrum. What force is required to move the rock?

Answer 1

Answer:

866.32 N

Explanation:

The diagram explains better.

Taking the total moment of forces, the sum of the clockwise moment of forces about the fulcrum must be equal to the sum of the anticlockwise moment of forces about the fulcrum:

F * (1.9 - 0.65) = 170 * 9.8 * 0.65

F * 1.25 = 1082.9

F = 1082.9/1.25

F = 866.32 N

A force of 866.32 N is needed to move the rock.