Re: [Phys-l] Student Misconceptions

[Philip Keller <PKeller@holmdelschools.org>]

I think we really need to know how and when the mass was added.  But if mass is added at the highest point and with an initial velocity of zero, I don't see why the amplitude would be affected.  And if it was added at the lowest point, well, how?  If the mass was stationary when it met the moving pendulum, then amplitude decreases.  But if it were added with the an initial velocity equal to the max. velocity of the pendulum, then again, I don't see why the amplitude would change.  But all of this seems kind of basic to me, which makes me suspect that I am completely missing the point of your question.  Can you tell what context motivates this?  And again, what mechanism increases the mass?

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of chuck britton
> Sent: Friday, October 07, 2011 8:53 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Student Misconceptions
>
> I'll take a stab at this.
>
> If the mass miraculously increases at the instant that the bob is at
> it's lowest point, then the amplitude will decrease.
>
> If the mass miraculously increases when the bob is at it's highest
> point, then the amplitude will increase.
>
> Am I missing something?  (except for maybe someone else's response -
> further down the mailbox?)
> .
> At 12:08 PM -0700 10/5/11, Bernard Cleyet wrote:
> > Aaa, perhaps Alphonsus' misreading of my request is a clue as to why
> > I've not received a response.
> >
> > My request was (is) what happens to the amplitude of a pendulum
> > clock when the bob's mass is increased (without changing the CoM).
> >
> > Not more misconceptions.
> >
> > bc frustrated.
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