- #1
aliaze1
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Torque/Static Equilibrium/Forces problem...
I have been working on this problem for a few hours, but I just can't get it ...
A 3.0-m-long rigid beam with a mass of 100 kg is supported at each end. An 80 kg student stands 2.0 m from support 1. How much upward force does support 1 exert on the beam?
here is an image:
http://photo.ringo.com/208/208651783O865465193.jpg
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τ=Frsinφ
F=ma
I figured out the torques kinda, but do i use the mass as (2/3*100)+80? or (2/3*100)+40...either way i kept getting a wrong answer...
and the center of mass i assume is where the person is right? bec the 80kg addition would be the most massive point right?
since the angles are 90 degrees, the sine of φ doesn't matter right?, i mean it would only affect the sign +/- of the answer...since τ=Frsinφ, and φ is either 90 or -90 degrees...
idk...basically i just can't get this...
i got solutions ranging from 76.666.., 1306.666... etc...
I have been working on this problem for a few hours, but I just can't get it ...
Homework Statement
Problem:A 3.0-m-long rigid beam with a mass of 100 kg is supported at each end. An 80 kg student stands 2.0 m from support 1. How much upward force does support 1 exert on the beam?
here is an image:
http://photo.ringo.com/208/208651783O865465193.jpg
----
Homework Equations
τ=Frsinφ
F=ma
The Attempt at a Solution
I figured out the torques kinda, but do i use the mass as (2/3*100)+80? or (2/3*100)+40...either way i kept getting a wrong answer...
and the center of mass i assume is where the person is right? bec the 80kg addition would be the most massive point right?
since the angles are 90 degrees, the sine of φ doesn't matter right?, i mean it would only affect the sign +/- of the answer...since τ=Frsinφ, and φ is either 90 or -90 degrees...
idk...basically i just can't get this...
i got solutions ranging from 76.666.., 1306.666... etc...
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