Moment of inertia / torque question

AI Thread Summary
The discussion revolves around calculating the total moment of inertia for a wheel and disk system, using the formula I1 + I2 = [(1/2) M1 * R1^2] + [M2 * R2^2]. Participants clarify the components of the moment of inertia, specifically mentioning the hoop and disk contributions. There is confusion regarding the correct formulas for moment of inertia and torque, with some questioning the validity of the calculations presented. The importance of clearly stating the original question for effective assistance is emphasized, along with a reminder that homework-related queries should be posted in designated sections. The conversation highlights the complexities of understanding torque and moment of inertia in physics.
ptlffrty
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ummm. i think you mean to say it is attached to a solid 'brick'
\vec{\tau} = \vec{r} \times \vec{F}
where \vec{r} is the position vector from the axis of rotation to where the force is acting, and \vec{F} is the force.
the direction of the vector produced by the cross product is given by the right hand rule.
 
oops. i meant disk.
 
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bump bump bump
 
anyone? anyone?
 
ptlffrty said:
a. what is the total moment of inertia of the wheel and disk?
I1 + I2 = [ (1/2) M1 * R1^2 ] + [ M2 * R2^2 ]
= (1/2)(6)(.1^2) + (2)(.5^2) = .53

One qn.. How did u actually arrive at this?
 
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added the moment of inertia of the hoop (mr^2) witht he moment of inertia of the disk (.5mr^2).. good chance its wrong, but itdoesnt really matter at this point, i just turned the assignment in a few minutes ago
 
Moment of inertia shld be the same as the formula for torque=F*d=mgd.
I'm not sure bout it either. But are u sure mr^2 is the right formula for moment of a force?
 
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You deleted the original question. How are we going to help if we don't know what you are asking? However, if it is a homework problem, it belongs in the homework section.
 
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