A balanced lever has two weights on it, the first with mass 3 kg and the second with mass 1 kg. If the first weight is 7 m from the fulcrum, how far is the second weight from the fulcrum?

1 Answer
Jan 3, 2016

21m

Explanation:

We apply the second condition for static equilibrium which states that the result torque (moments) must be zero,
ie. sum vectau=0, where vectau=vecrxxvecF is the cross product of the position vector from the axis of rotation (fulcrum) to the applied force and the applied force.

So in this case :

r_1F_1-r_2F_2=0

therefore (7xx3g)-(r_2xx1g)=0

thereforer_2=(7xx3xx9.8)/(1xx9.8)=21m.