Which has the larger moment of inertia?

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SUMMARY

The discussion centers on the comparison of the moment of inertia between a uniform disk and a bicycle wheel with spokes, both having the same mass (M) and radius (R). The bicycle wheel has a larger moment of inertia due to its mass being concentrated at a larger radius, resulting in a higher integral value for the moment of inertia calculation, specifically \(\int{dm*r^2}\). The solid disk, with more mass located closer to the center, has a lower moment of inertia, calculated as \(\frac{1}{2}MR^2\), compared to the bicycle wheel's moment of inertia, which is greater due to its structure.

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  • Understanding of moment of inertia and its mathematical definition
  • Familiarity with the concepts of mass distribution in rigid bodies
  • Knowledge of integral calculus as it applies to physics
  • Basic principles of rotational dynamics
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eraemia
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Homework Statement



Two wheels have the same total mass M and radius R. One wheel is a uniform disk. The other is like a bicycle wheel, with lightweight spokes connecting the rim to the hub. Which has the larger moment of inertia?

a. The solid disk
b. The wheel with spokes
c. There is insufficient unformation for a meaningful answer

Homework Equations





The Attempt at a Solution



the solid disk because it has less surface area / holes for air friction?
 
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Think about the definition of moment of inertia... it is \int{dm*r^2}
 
ok so the thin spherical shell would have a moment of inertia of 2/3 MR^2
whereas the solid sphere would have 2/5 MR^2

therefore the bicycle has more inertia
 
eraemia said:
ok so the thin spherical shell would have a moment of inertia of 2/3 MR^2
whereas the solid sphere would have 2/5 MR^2

therefore the bicycle has more inertia

Yes, exactly right. More of the mass is concentrated at a larger radius in the bicycle...

For the uniform disk, a lot of the mass is in between 0 and R... but for the bicycle most of it is located around R... so the integral dm*R^2 is higher for the bicycle.
 
alright, i think i get it now. thanks
 

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