Rotational Inertia: Mass Distribution & Rolling Object Comparison

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Discussion Overview

The discussion revolves around the concept of rotational inertia, specifically comparing the rotational inertia of a hoop and a solid sphere of the same mass when rolled. Participants explore how mass distribution affects rotational inertia, particularly in the context of angular acceleration and torque.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • Some participants propose that the rotational inertia of an object is influenced not only by its mass but also by how that mass is distributed relative to the axis of rotation.
  • One participant argues that a hoop has all its mass at a fixed distance from the axis, suggesting it has a higher moment of inertia compared to a solid sphere, which has mass distributed closer to the axis.
  • Another participant elaborates on the relationship between mass distribution and angular acceleration, noting that mass farther from the center of rotation experiences greater acceleration, which is relevant for calculating rotational inertia.

Areas of Agreement / Disagreement

Participants express differing views on the comparison of rotational inertia between the hoop and the solid sphere, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

The discussion does not resolve the mathematical implications of the claims made regarding rotational inertia, nor does it clarify the specific definitions of terms used, such as "moment of inertia" and "angular acceleration." There are also assumptions about the radius of the objects that are not explicitly stated.

RPDuece
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Help with this problem...

The Rotational inertia of an object depends not on the mass alone but on the distribution of the mass. Between a hoop and a solid sphere of the same mass which object has higher rotational inertia when they are rolled? Explain how the distribution of the mass affects rotational inertial.
 
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Intuitively, the further away the mass is from the axis of rotation, the higher the moment of inertia.
In a hoop all the mass is distributed at a fixed distance.
In a sphere there is mass closer to the axis of rotation (assuming it has the same radius as the hoop), so its moment of inertia will be lower.
 
Thank you that helps a lot...
 
RPDuece said:
Help with this problem...

The Rotational inertia of an object depends not on the mass alone but on the distribution of the mass. Between a hoop and a solid sphere of the same mass which object has higher rotational inertia when they are rolled? Explain how the distribution of the mass affects rotational inertial.
The elements of matter contained in rigid body experiencing angular acceleration (ie. a torque acting on it) have different accelerations depending on their distance from the centre of rotation (centre of mass). The mass that is farther from the centre is accelerated more rapidly than mass closer to the centre. So to determine what angular acceleration results from a given torque, one has to compute the rotational inertia of the body, which depends on the distribution of mass in relation to the centre of mass.

AM
 

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