A balanced lever has two weights on it, the first with mass #14 kg # and the second with mass #9 kg#. If the first weight is # 2 m# from the fulcrum, how far is the second weight from the fulcrum?

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Answer 1 · 2017-03-07T07:16:09

#3.1m#

A moment is the product of force and the distance over which the force acts.

#M = Fd#

In a balanced lever, both moments are equal to each other, so

#M_1 = M_2#

#F_1d_1 = F_2d_2#

We can work out the force either side by #F=ma#, where #a~~10ms^-2#, so

#F_1 = 14 xx 10 = 140N#

#F_2 = 9 xx 10 = 90N#

and put these values, along with #d_1 = 2m# (from the question) into the equation:

#2m xx 140N = d xx 90N#

#d = 280/90 = 3.1m#