Re: Angular momentum

in article [EMAIL PROTECTED], Richard at [EMAIL PROTECTED]
wrote on 10/25/03 5:05 PM:

> 
> 
> Timtro wrote:
>> 
>> I'm sorry to bother you all with this question. I was just playing around
>> with a problem I found in a book. It is a simple problem where in a man sits
>> on a stoll free to ratate without friction and is spun around while he holds
>> two 3kg weights. we are given the moment of inertia of the man+stool,
>> initial speed and the fact that the weights are 1m from the axis of
>> rotation. The man then contracts his arms to 0.3m from the axis of rotation.
>> Obviously the man will go faster because of this, but when I calculated the
>> initial and final kinetic energies, they were VERY differant. Where did all
>> that extra energy come from? Or did I calculate the energy wrong?
> 
> The man had to do work to reel in the weights.

One of my pet interests is fly fishing and the cazsting required to   put a
fly out where you want it to go. The process is similar to that used in a
whip.

A heavy line, ususally tapered in thickness, is flicked out using arm
motion. After the flick (cast) is completed, arm motion ceases. The line
continues to travel. The speed of the tip can increast (in the case of a
whip) close to the speed of sound. Often, the whip cracks or a fly gets
flicked of the leader.

How does the tip get speeded up? Aside from incidental losses to sound and
the like, is mechanical energy conserved? Is momentum conserved? If not,
where does extra momentum com from?

If there is a discussion on the subject here, and if no one figures it out
(an unlikely situation) I will reveal the mechanisms in a week or two.

Bill