SOLUTION: PLEASE HELP A 3m bar is used to lift a stone . A 90 kg person exerts all his weight to one end of the bar which is 2 1/2 m from the fulcrum and balances the stone. The weight of t

Algebra ->  Inverses -> SOLUTION: PLEASE HELP A 3m bar is used to lift a stone . A 90 kg person exerts all his weight to one end of the bar which is 2 1/2 m from the fulcrum and balances the stone. The weight of t      Log On


   

Question 181305: PLEASE HELP
A 3m bar is used to lift a stone . A 90 kg person exerts all his weight to one end of the bar which is 2 1/2 m from the fulcrum and balances the stone. The weight of the stone is approximately?
a. 500
b. 450
c. 400
d. 45 kg.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Set up a moment (force x distance) equilibrium equation.
F%5B1%5Dd%5B1%5D=F%5B2%5Dd%5B2%5D
.
.
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Find the associated distances from the pivot for both forces.
d%5B1%5D=2.5
d%5B1%5D%2Bd%5B2%5D=3
d%5B2%5D=0.5
.
.
.
The force, in this case, is gravity,
F=mg
m%5B1%5Dgd%5B1%5D=m%5B2%5Dgd%5B2%5D
m%5B1%5Dd%5B1%5D=m%5B2%5Dd%5B2%5D
90%282.5%29=m%5B2%5D%280.5%29
m%5B2%5D=90%282.5%2F0.5%29
m%5B2%5D=90%2A5=450
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.
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B.)450 kg.