A balanced lever has two weights on it, the first with mass #12 kg # and the second with mass #4 kg#. If the first weight is # 15 m# from the fulcrum, how far is the second weight from the fulcrum?
Since, the lever is balanced about the fulcrum i.e. net moment about fulcrum must be zero.
Now, taking moment of both the masses about the fulcrum as follows
For a balanced lever, we have the relationship:
#m_1,m_2#are the masses of the two weights
#d_1,d_2#are the distances the weights are from the fulcrum
So, we get: