Angular speed of a swinging rod

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Homework Help Overview

The problem involves a nonuniform rod that swings from a horizontal to a vertical position, requiring the determination of its angular speed at the vertical position. The context includes concepts from rotational dynamics and energy conservation.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of conservation of energy and question the correct height to use for potential energy calculations. There is uncertainty about how to determine the change in height of the center of mass during the swing.

Discussion Status

The discussion is active, with participants exploring the relationship between the initial and final positions of the center of mass. Some guidance has been provided regarding the importance of the center of mass's height change, and one participant expresses understanding after receiving assistance.

Contextual Notes

Participants are navigating the specifics of the problem setup, particularly regarding the height of the center of mass and its implications for energy calculations. There may be assumptions about the uniformity of the rod that are not fully addressed.

chouZ
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Homework Statement


A nonuniform 2-0 kg rod is 2.0 m long. The rod is mounted to rotate freely about a horizontal axis perpendicular to the rod that passes through one end of the rod. The moment of inertia of the rod about this axis is 4.0 kg.m2. The center of mass of the rod is 1.2 m from the axis. If the rod is released from rest in the horizontal position, what is its angular speed as it swings through the vertical position?


Homework Equations




The Attempt at a Solution



I tried to use conservation of energy but I am not really sure whether the height in the potential energy initially is the distance from the center of mass to the rotational axis or the length of the rod...?:confused:
 
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In calculating the change in gravitational PE of the rod, what matters is the change in height of its center of mass.
 
still a lit bit confused...the change in height..how can u calculate it? I mean I thought about it: the height h between the position of the center of mass initially and its position at the final moment...but i can find a way to find the answer...
 
Think it through. When the rod is horizontal, where is its center of mass? What about when it swings down to be vertical? Draw yourself a picture and figure out the change in height.
 
got it...thanks for the help!
 

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