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Author | Topic: Counter-Intuitive Science | |||||||||||||||||||
New Cat's Eye Inactive Member |
Once I was walking towards a set of sliding doors. I noticed them open and close for a group of people walking ahead of me, but when I came to them they wouldn't open. Judging that the sensors weren't sensitive enough to detect my modest weight, I decided to leap vertically in the air in the hope that when I came down the extra force of my impact would open the doors. It did not, and couldn't have done. Why not? Because it employed an optical sensor and not a pressure one.
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New Cat's Eye Inactive Member |
. If the rope is longer so the marine can put the rope at an angle by walking a few feet away from the grandpa he can lift the grandpa if he is strong enough Not if he's standing on ice... There's gonna be a horizontal component to the force that the friction between his feet and the ground will have to overcome.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
Because it employed an optical sensor and not a pressure one. Obviously I'd have been wrong if I'd been wrong about how the door worked. But I'd also have been wrong if I'd been right about how the door worked (which I was).
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slevesque Member (Idle past 4662 days) Posts: 1456 Joined: |
I never do well with these kind of questions:
I think it could have at the moment you jump, since you are pushing on the ground to get yourself a vertical, upward acceleration. Couldn't when you came down since the only force in play is your weight (and the normal force of the ground)
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dwise1 Member Posts: 5949 Joined: Member Rating: 5.5 |
I believe that motion detectors are much more common nowadays than pressure pads, which I don't think I've even seen since my childhood 40 years ago. Assuming that it requires detecting motion towards it, jumping vertically would not involve any motion towards it and so should not trigger it. As for why it didn't detect your initial approach, I don't know, unless you arrived in some time interval when it's designed to not look, such as when it has opened for someone, at which time a different sensor would keep it from closing until after the last person had entered. Did you approach from a highly oblique angle? Though when I do that to a door, it still detects me. Many even detect me walking past; must be my electro-magnetic personality.
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Iblis Member (Idle past 3918 days) Posts: 663 Joined: |
I'm a little baffled. You seem to be saying that the door did detect pressure on the ground. If so, yeah, you should have been able to knock this over whatever minimum was required by jumping on it.
Calling this pressure "weight" shouldn't make any difference. Standard scales, the spring and lever kind for example, veer up all out of proportion when you jump on them. Some sort of stable mass-register, might not, but, what in the world ... my imagination starts to fail me at this point. Give.
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ringo Member (Idle past 434 days) Posts: 20940 From: frozen wasteland Joined: |
Catholic Scientist writes:
Yes, it becomes a complex vector problem with no easy intutitve answers. There's gonna be a horizontal component to the force that the friction between his feet and the ground will have to overcome. "I'm Rory Bellows, I tell you! And I got a lot of corroborating evidence... over here... by the throttle!"
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New Cat's Eye Inactive Member |
Yes, it becomes a complex vector problem with no easy intutitve answers. Just create a free body diagram in your head
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ringo Member (Idle past 434 days) Posts: 20940 From: frozen wasteland Joined: |
Catholic Scientist writes:
Yes, the first step is to recognize that you need to analyze the problem, not just jump to the "obvious" conclusion that the stronger man wins. Just create a free body diagram in your head "I'm Rory Bellows, I tell you! And I got a lot of corroborating evidence... over here... by the throttle!"
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CosmicChimp Member Posts: 311 From: Muenchen Bayern Deutschland Joined: |
Could it be that the sensor was aiming at the other side of the sliding doors? Was it that you were using the doors but not in the proper direction; an entrance for an exit or vice versa?
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jar Member (Idle past 416 days) Posts: 34026 From: Texas!! Joined: |
Doubt it, that was tried back in Message 67.
Anyone so limited that they can only spell a word one way is severely handicapped!
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New Cat's Eye Inactive Member |
Yes, the first step is to recognize that you need to analyze the problem, not just jump to the "obvious" conclusion that the stronger man wins. I thought the "obvious" conclusion was that the heavier man wins... The marine *could* lift him if he could walk backwards with the rope and pulled at an angle.
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RAZD Member (Idle past 1427 days) Posts: 20714 From: the other end of the sidewalk Joined: |
That there are no green stars even though there is green light in their spectrum. there is a green blob ... or is it the green goblin? Science | AAAS Enjoy by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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ringo Member (Idle past 434 days) Posts: 20940 From: frozen wasteland Joined: |
Catholic Scientist writes:
I've actually done the experiment with a little guy who thought he was stronger than me. I thought the "obvious" conclusion was that the heavier man wins... "I'm Rory Bellows, I tell you! And I got a lot of corroborating evidence... over here... by the throttle!"
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RAZD Member (Idle past 1427 days) Posts: 20714 From: the other end of the sidewalk Joined: |
if you are bicycling and come to a stop light that senses vehicles, you can trip the sensor by laying your bike down over the sensor area (usually visible as a rectangle in the pavement) because they use electrical inductance, which falls off with distance squared ...
Enjoy by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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