Nellie Newton applies a force of 50 n to the end of a lever, which is moved a certain distance. If the other end of the lever moves one-third as far, show that the force it exerts is 150 n.

Make a simple sketch of the situation. It always helps.

You do know your formulae, right?

Moment of a force = Fd

Where F is the force applied and d is the perpendicular distance from the pivot. Since here the ratio of the distance done by the ends of the lever is the same as the ratio of the distance from the ends to the pivot, we can say that d here is also the distance the lever moved.

Now, since the moment of the force is the same everywhere (only one lever is involved), we get:

F_Nd_N = F_ld_l

Fn is force that Nellie applies
dn is the distance covered by Nellie
Fl is the force that the lever 'applies'
dl is the distance covered by the lever.

Find Fl, and you'll see it equals 150 N.

I hope it helps! :)

Thank you :)

Nice explanation, I appreciate that.

You're welcome :)