Counter-Intuitive Science

Because it employed an optical sensor and not a pressure one.

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.

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).

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)

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.

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.

Yes, it becomes a complex vector problem with no easy intutitve answers.

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"I'm Rory Bellows, I tell you! And I got a lot of corroborating evidence... over here... by the throttle!"

Just create a free body diagram in your head

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.

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"I'm Rory Bellows, I tell you! And I got a lot of corroborating evidence... over here... by the throttle!"

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?

Doubt it, that was tried back in Message 67.

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Anyone so limited that they can only spell a word one way is severely handicapped!

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.

there is a green blob ... or is it the green goblin?Science | AAASEnjoy

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we are limited in our ability to understand
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I've actually done the experiment with a little guy who thought he was stronger than me.

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"I'm Rory Bellows, I tell you! And I got a lot of corroborating evidence... over here... by the throttle!"

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

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we are limited in our ability to understand
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)