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Started By
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re: Can you solve this 2014 US Physics team qualifying exam helicopter rope problem?
Posted on 10/28/21 at 11:39 pm to Duane Dibbley
Posted on 10/28/21 at 11:39 pm to Duane Dibbley
It doesn’t matter how fast you’re moving. It will always be a straight line. It might be at a different angle but it will be a straight line.
0
Posted on 10/28/21 at 11:41 pm to euphemus
E is my guess
Posted on 10/28/21 at 11:42 pm to Ross
quote:
My intuition said B in a vacuum, D with air resistance
I’m a ME so if that’s wrong I will have to bare great shame
I’ve kind would be straight down if I’m a vacuum. If the helicopter could fly in a vacuum.
This post was edited on 10/28/21 at 11:43 pm
Posted on 10/28/21 at 11:45 pm to Ross
Veritasium actually did the experiment
https://www.youtube.com/watch?v=q-_7y0WUnW4
https://www.youtube.com/watch?v=q-_7y0WUnW4
This post was edited on 10/28/21 at 11:59 pm
Posted on 10/28/21 at 11:46 pm to euphemus
C
Posted on 10/28/21 at 11:51 pm to X123F45
quote:
Think of a flag blowing in the wind.
The waving of the flag is caused by vortices shedding off the flag pole.
The helicopter blades are sending quite a downdraft which will affect the top part of the cable the most. Those downdrafts would be coming in vortices. If it was a plane I would say “C”, because the weight of the rope is less and less as we move down the rope. Since it is a helicopter, the downward flow of air is the critical thing, and it is in the form of vortices, but much more complicated than the simple flag pole shedder. I guess it would be “D”, but that cable would have very complex waves running through it.
Posted on 10/29/21 at 12:18 am to DVinBR
I’ll have to believe it I sat down and did the free body diagram it might have been clearer to me, but my intuition clearly failed me there, probably because my brain assumed the rope behavior as though there was an end mass and couldn’t shake the notion there was an end mass
At least it seemed this simple problem stumps most.
At least it seemed this simple problem stumps most.
Posted on 10/29/21 at 12:50 am to Ross
most people don't know what the airflow is like around a helicopter, people just think that it's so much air movement that it's able to lift a multi ton vehicle, then it MUST push enough air down to affect the rope, but that's not the case
Posted on 10/29/21 at 12:55 am to euphemus
B then the video 2nd scenario is D. Got the both correct. BS in Physics 1973.
Posted on 10/29/21 at 12:58 am to euphemus
Posted on 10/29/21 at 2:17 am to euphemus
what are you, my final?
Posted on 10/29/21 at 3:51 am to euphemus
My initial answer was B but then I thought that seemed too easy for the test so I changed it to C figuring there was some rotor wash frickery. One of these days I'll learn to stop second guessing myself.
Posted on 10/29/21 at 4:04 am to euphemus
C
Posted on 10/29/21 at 4:16 am to euphemus
the real question is , how does the rope FEEL being subjugated by the chopper, does the point of attachment respresent the patriarchy
Posted on 10/29/21 at 4:24 am to euphemus
After seeing plenty of sling loads and a rope extraction exercise once, I am going to say B if the helicopter is flying horizontally at a constant speed. Then again there are weighted objects at the end of the rope. I don't know, it has been a long time since I have seen anything physics ,and B is my best educated guess.
This post was edited on 10/29/21 at 4:27 am
Posted on 10/29/21 at 5:17 am to euphemus
Ask her.
She can tell you the answer.
She can tell you the answer.
Posted on 10/29/21 at 5:52 am to euphemus
C
edit.... well shite. Watch the video a few posts above.
edit.... well shite. Watch the video a few posts above.
This post was edited on 10/29/21 at 5:56 am
Posted on 10/29/21 at 6:00 am to Ross
quote:
My intuition said B in a vacuum, D with air resistance
I’m a ME so if that’s wrong I will have to bare great shame
same answer for me. im a ChE
Posted on 10/29/21 at 6:03 am to euphemus
B
A nylon balloon drifting with a string is diagonal from the baloon
A nylon balloon drifting with a string is diagonal from the baloon
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