How Do You Calculate the MOI for a Rod with a Mass Attached?

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To calculate the moment of inertia (MOI) for a rod with an attached mass, use the formula for a rod rotating about one end, which is (1/3) * m * L^2, where m is the mass of the rod and L is its length. For the attached mass, apply the parallel axis theorem, which states that the MOI of the mass is its own MOI plus the product of its mass and the square of the distance from the axis of rotation. In this case, the distance is 0.75 m from the end of the rod to the washer. Combine the MOIs of both the rod and the washer to find the total MOI of the system. This approach will yield the correct MOI for your lab assignment.
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Sorry about the somewhat extreme thread but I'm sort of desperate. I missed nearly the whole rotation unit cause of illness and I need to find the MOI for a lab that's due tomorrow. I'm confused about what to plug in where. The lab goal is to find the MOI of a rod of uniform density swinging with a point of rotation at the end of the rod. The rod has a mass attached about 3/4 the way down the rod from the point of rotation. The mass is a circular washer and is about 20 g in weight. The rod is 1 m long and weights 97.1 g. How do you find the MOI of the rod/mass complex

Thanks!
 
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user_name12 said:
Sorry about the somewhat extreme thread but I'm sort of desperate. I missed nearly the whole rotation unit cause of illness and I need to find the MOI for a lab that's due tomorrow. I'm confused about what to plug in where. The lab goal is to find the MOI of a rod of uniform density swinging with a point of rotation at the end of the rod. The rod has a mass attached about 3/4 the way down the rod from the point of rotation. The mass is a circular washer and is about 20 g in weight. The rod is 1 m long and weights 97.1 g. How do you find the MOI of the rod/mass complex

Thanks!

Welcome to the PF. Hope you're feeling better.

This resource should help you out:

http://en.wikipedia.org/wiki/Moment_of_inertia

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