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Ruler torque question

  • Thread starter ph4all
  • Start date
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1. Homework Statement
A 30 cm ruler has a mass of 5g. Mark the pivot point and calculate the torque for the following situation:

Ruler extends 10cm out from desk


2. Homework Equations
T= r x F

F= |F|sinΘ

F= m Fg

3. The Attempt at a Solution

F= mFg
= (0.005kg) (9.8 m/s^2)
=0.049 N

T= r x F
=|r||F|sinΘ
=(0.10m)(0.049N) sin 90 degrees
=0.00049 Nm

The only thing Im not sure on is that only a third of the ruler is hanging off the desk so I am not sure if I have divide the mass.
 

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