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Date Posted: 12/3/2007 6:19:56 AM  Status: Live
Need help before final!!!
Course Textbook Chapter Problem
Classical Mechanics Vector Mechanics for Engineers: Statics and Dynamics (8th) by Beer, Johnston, Eisenberg 16 112P
Question Details:
   Hi, I've tried solving this probelm, but I can't figure out what I'm doing wrong. I dont know if the acceleration at G is ax=mrα or if their is an angle, i.e. ax=m(rsinθ)α. Also I dont know what ay is. Can someone help?
 
 
 
 
The 16-lb uniform slender rod AB is supported by a small wheel at C and end A can slide on the horizontal surface. Knowing that the rod is released from rest in the position shown and neglecting friction at A and C, determine immediately after release (a) the angular acceleration of the rod, (b) the reaction at point A.
 
 
 
 
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Date Posted: 12/3/2007 10:54:04 AM  Status: Live
Asker's Rating: Lifesaver   
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ME 214's Comment:
Big life saver!!!

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Date Posted: 7/23/2008 4:36:53 PM  Status: Live
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I just wanted to point something out about the above solution.  Although the equations are correct, the free body diagram is wrong, or at least inconsistent with with your equations. 

There should be a normal force perpendicular to rod AB acting at point C (caused by the wheel).  And the reactive force at A should be vertical, not perpendicular.

The reason this is a big deal is because of the equation that sums the moments about point P.  If the reactive force at A were slanted as shown in the FBD, there would be a moment caused by that force with a 16 inch radial arm.  The equation shows only a moment caused by weight.

 The only way for the equation to be correct, and consistent with the FBD is for the normal force at C and the reactive force at A to intersect at point P, therefore neither causes a moment.



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