What is the minimum force F must be applied to lift the body mass m? The height of the inclined plane is equal to H and the length of the inclined plane is equal to L. Consider the blocks to be weightless and neglect friction.
Solution. Posted on Saturday, December 27, 2014.
If a movable pulley moved a distance l than the force F performed work equal to F*l. The body on the inclined plane at the same time moved a distance 2*l and rose to a height of h. The amount of gravitational potential energy (m*g*h) possessed by an elevated the body is equal to the work done. Thereby, m*g*h=F*l. The h could be found from the similarity of triangles.
h = 2*l*H/L
Now, when looking at the previous equation, it can be written as m*g*2*l*H/L=F*l