Posted by PhysicsCrazy<3 on .
A boy exerts a force of 210 N on a lever to raise a 1.25 103 N rock a distance of 12 cm. If the efficiency of the lever is 88.7%, how far did the boy move his end of the lever?
Thanks for all your help :)
<3,
PhysicsCrazy<3

physics 
drwls,
Work done on the rock will be 87% of the work performed by the boy.
210N*X = 0.87*1250N*0.12m
Solve for X