The ideal mechanical advantage of a slope is given by the ratio between the output load, which is simply the weight of the object ([tex]F_w[/tex]), and the input force [tex]F_i[/tex] applied to move the object along the slope:
[tex]ima= \frac{F_w}{F_i} [/tex]
The energy conservation law states that the potential energy of the object when it reaches the final height h is equal to the work done to move the object along the distance of the slope [tex]l[/tex], i.e.
[tex]F_w h = F_i l[/tex]
From this we find
[tex] \frac{F_w}{F_i} = \frac{l}{h} [/tex]
Therefore, we can substitute this into the formula of the ideal mechanical advantage and calculate its value:
[tex]ima= \frac{l}{h} = \frac{120~m}{40~m}=3 [/tex]
