Physics Help Please

Question

A man uses a rock as a fulcrum and lifts a 300-kg boulder with a metal bar 6.00 m long. Calculare the force necessary to lift the boulder if the fulcrum is:

(a) 1.00 m from where the bar contacts the rock.

(b) 3.00 m from where the bar contacts the rock

Answer 1

Jack, I have a feeling that you forgot to give the mass of the metal bar, which is important for case (a).

Please check again the problem, and if it is the case, then add this info.

In case (b) you just use the equation

F (L - l) = mgl,

where

L = 6 m - length of the bar,

l = 1 m - distance between the rock and boulder,

m = 300 kg - mass of the boulder,

g = 10 m/s² - acceleration due to gravity.

Then F = mgl / ( L - l)