The Whip Effect

[Paul Arden]

I was looking at Tobias’ video here...

[media] [/media]

I was wondering how reverse torque affects the whip effect? Or is that a blind alley?

Any other comments on the video?

Cheers,
Paul

[Paul Arden]

Incidentally with the pirouette effect one would expect to be able to rotate a softer rod faster, which is most certainly not the case. Indeed the opposite is true.

Cheers, Paul

[Graeme H]

It doesn't ring true to me.

Cheers,
Graeme

[James9118]

What about the Welsh helicopter effect?

[Paul Arden]

Well I don’t know about that. But I would like to see a discussion about it. I can sort of understand the whip; in my mind it’s very close to Spring. And I know we’ve gone around it before but I want to go around it again.

James, as far as I’m concerned you’re the no.1 physicist on this Board and so I would love to know your opinions on this/these subjects.

Many thanks,
Paul

[hshl]

Hi Paul
we've had discussions about the whip effect on this board and maybe it is worth to read them again?! The video contains nothing new, it tries to give a more differentiated view on the redistribution of angular momentum.

Cheers

[gordonjudd]

it tries to give a more differentiated view on the redistribution of angular momentum.

Tobias,

How are you calculating the angular momentum of a flexible rod?

Since different 5cm sections of the rod would have different moments of inertia and angular velocities I would think the composite angular momentum of the rod would be difficult to calculate.

Gordy

[Paul Arden]

Ok well let me see if I can explain it “the whip effect” in my own words and you can tell me how far away I am from understanding it

Because the rod unloads from butt to tip, and because the rod is tapered (decreasing mass), as it unloads a wave travels from the rod butt to the tip which results in a higher tip speed than the spring alone...?

(There are two topics here but let’s deal with this one first).

Thanks, Paul

[Bianchetti Ivan]

This is what I see rotating behind, the loop is more closed and the tendency to create a curve on the line is less, I find at the time of going back the possibility of having the weight available immediately, could it be just a muscle? Or an additional acceleration before the barrel straightens? Maybe due to the simple rotation of the linear rather than circular wrist?

[Paul Arden]

I think that’s the Torque Twist thread, Ivan?

The second question I have is back to my original observation on the “pirouette effect”. I can fully understand that the shortening of the lever means that we can rotate faster however when one compares a stiff rod, even going as far as to cast a rigid lever, the speed we can rotate the rod is far higher than a softer rod. So while the effect is undoubtedly there, I think it’s a bit misleading.

But I’m mostly interested in a better understanding of the whip effect.
http://www.sexyloops.com/pdf/SwingSpringWhip.pdf

Sorry I know it must be frustrating to have to explain it over and over again. But I don’t fully understand it and I know I’m not alone.

Cheers, Paul