Moment of inertia rolling down a hill

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Homework Help Overview

The discussion revolves around the moment of inertia of two solid spheres rolling down a hill and which one reaches the bottom first. The original poster expresses confusion regarding the influence of mass and moment of inertia on the outcome.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the effects of mass and moment of inertia on the motion of the spheres, questioning the role of gravity and angular velocity. There are attempts to clarify the physics involved in rolling without slipping.

Discussion Status

The discussion is ongoing, with participants providing guidance on the physics concepts involved. Some participants are questioning assumptions about the relationship between mass, radius, and the time taken to reach the bottom of the hill.

Contextual Notes

There are indications of varying levels of understanding among participants, with some expressing difficulty in grasping the concepts due to perceived inadequacies in instruction. Links to external resources have been shared for further exploration.

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Homework Statement



Two solid spheres -- a large, massive sphere and a small sphere with low mass -- are rolled down a hill. Which one reaches the bottom of the hill first?

Homework Equations



ICM= (2/5)MR2

The Attempt at a Solution



I thought that this would be the smaller sphere because it has a lower moment of inertia… but this isn't right. Can someone please explain?
 
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You have to do the physics ... what are the forces on the cylinders and the constraints?
Have you just done a lesson or so on rolling without slipping?
 
What physics do I have to do? My teacher talked about it a little… but honestly he is not very good at explaining things so I am having trouble understanding this.
 
Just gravity is acting on them right? So the larger, more massive one would reach the bottom first?
 
The wheel has to roll as well - so it will have an angular velocity.
Have a look at how other's do it.
http://faculty.wwu.edu/vawter/PhysicsNet/Topics/RotationalKinematics/RollingWithoutSlipping.html
https://www.physicsforums.com/showthread.php?t=169313
... there are also video tutorials on youtube.
 
Last edited by a moderator:
okay so since the masses and radii drop out, they reach the bottom at the same time?
 
why would the masses and the radii "drop out" - did you do any math?
 
that's what it was on your second example… What math am I supposed to do??
 
Have you had a look at the links I have given you?
 

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