• Support PF! Buy your school textbooks, materials and every day products Here!

Ruler torque question

  • Thread starter ph4all
  • Start date
  • #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

Homework Equations

T= r x F

F= |F|sinΘ

F= m Fg

The Attempt at a Solution

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

T= r x F
=(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.

Answers and Replies