Rotational Kinetic Energy Problem

Click For Summary

Homework Help Overview

The discussion revolves around a problem involving the rotational kinetic energy of a thin uniform-density rod, which is rotating about an axis perpendicular to its length. The problem includes specific parameters such as mass, length, angular speed, and linear speed, and asks for both rotational and total kinetic energy calculations.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the equation for rotational kinetic energy and the moment of inertia, with some questioning the validity of the formulas being used. There are attempts to clarify the correct moment of inertia for the rod and its application in the context of the problem.

Discussion Status

The discussion is ongoing, with participants actively questioning the equations and attempting to clarify the correct approach to calculating the moment of inertia for the rod. There is no explicit consensus yet, but guidance on the correct moment of inertia has been introduced.

Contextual Notes

Participants are navigating through potential misunderstandings regarding the equations for rotational kinetic energy and moment of inertia, indicating a need for clarity on these concepts. The original poster has provided specific numerical answers, which may influence the direction of the discussion.

Loppyfoot
Messages
192
Reaction score
0

Homework Statement



A thin uniform-density rod whose mass is 3.8 kg and whose length is 3.0 m rotates around an axis perpendicular to the rod, with angular speed 34 radians/s. Its center moves with a speed of 10 m/s.

(a) What is its rotational kinetic energy?
(b) What is its total kinetic energy?


Homework Equations



Well I know that Krot= 1/2I* w2. But when I try to use this equation, I get the wrong answer. I also know that I= 1/2mr^2

The correct answers are:

(a)= 1650 J
(b)= 1840 J

Does anyone have any idea on where I'm going wrong?

The Attempt at a Solution

 
Physics news on Phys.org
Loppyfoot said:
I also know that I= 1/2mr^2

from where did you get this?
 
Moment of Inertia= mr^2. Sorry.
 
How did you get that?
 
That's not the equation? Then what equation would I use to represent the rod with moment of inertia?
 
moment of inertia of a uniform rod is ml^2/12 about its center of mass.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
Replies
9
Views
3K
  • · Replies 33 ·
2
Replies
33
Views
3K
  • · Replies 21 ·
Replies
21
Views
5K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 16 ·
Replies
16
Views
2K
Replies
2
Views
1K