The Board

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

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

It doesn't ring true to me.

Cheers,
Graeme

What about the Welsh helicopter effect?

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

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

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

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

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?

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