Standing on hands...lose weight?

[pthebutcher]

Not necessarily. Aren't the scales used for weigh in usually balance beam scales? These scales measure mass.

Thats true, my bad. In which case i will now believe that this is clearly a myth. The only mass leaving the system is moisture through your breath and the reactions within your body converting mass to energy. This amount of mass would be well outside the accuracy of the scale. Like CyinCo suggested, this is likely variability in the scale.

 

[CyinCo]

Thats true, my bad. In which case i will now believe that this is clearly a myth. The only mass leaving the system is moisture through your breath and the reactions within your body converting mass to energy. This amount of mass would be well outside the accuracy of the scale. Like CyinCo suggested, this is likely variability in the scale.

Sounds like a good Mythbusters episode.

Anyone been seeing the MacGyver shorts? Good stuff.

 

[mt85]

Assuming you take an enclosed semi trailer and load it with 100 pigeons. Will it weigh less if all of the pigeons are airborne with in the trailer as opposed to sitting on the floor of the trailer?

 

[CyinCo]

Assuming you take an enclosed semi trailer and load it with 100 pigeons. Will it weigh less if all of the pigeons are airborne with in the trailer as opposed to sitting on the floor of the trailer?

The trailer will not weigh less. The weight may flucuate. The birds fly by pushing off of the air in the trailer. The air in the trailer will, in turn, push on the trailer. There will be no change. Didn't they do this one on Mythbusters?

 

[mt85]

The trailer will not weigh less. The weight may flucuate. The birds fly by pushing off of the air in the trailer. The air in the trailer will, in turn, push on the trailer. There will be no change. Didn't they do this one on Mythbusters?

Yes, and the weight remained the same because their was no change in mass that was contained within the truck. This should help answer the question about this myth as well. Standing on ones hands before stepping on a scale will not change ones weight.

 

[CyinCo]

Not true. They are overcoming gravity by flapping their wings. The wings interact with the air in the trailer to give them lift but the air in the trailer interacts with the trailer. You can't think of the tailer as empty simply because it is air between the birds and the trailer. The effects of the air on the trailer and the birds is real.

To think of this another way, imagine the trailer contains a vacuum and the birds could somehow survive. Could they fly? No, because their flight requires the volume of air.

Edit: This was a reply to another post that seems to no longer be there.

 

[jdoggivjc]

Yes, and the weight remained the same because their was no change in mass that was contained within the truck. This should help answer the question about this myth as well. Standing on ones hands before stepping on a scale will not change ones weight.

First, the myth wasn't about the difference between the mass of the truck when the birds were in rest compared to when the birds were in flight, the myth was about whether the birds flapping their wings created some kind of "lift" that made the truck itself lighter.

That being said, the problem they eventually ran into with this myth is they couldn't make sure the birds stayed in the air the entire time with the fan that they used, and they had to use that style of fan at the speed they did because they couldn't use something bigger/badder without risking the lives of the birds.

How they eventually tested the "lift" theory (not the mass theory) was they built a helicopter and flew it in the truck, and it did not create this magical "lift" to make the truck lighter.

But in the end, the myth wasn't testing the mass of a closed system and the effects of the birds resting/flying around in that closed system, it was testing the myth that the birds flying around affected the weight of the truck itself. Which it did not.

 

[CyinCo]

First, the myth wasn't about the difference between the mass of the truck when the birds were in rest compared to when the birds were in flight, the myth was about whether the birds flapping their wings created some kind of "lift" that made the truck itself lighter.

That being said, the problem they eventually ran into with this myth is they couldn't make sure the birds stayed in the air the entire time with the fan that they used, and they had to use that style of fan at the speed they did because they couldn't use something bigger/badder without risking the lives of the birds.

How they eventually tested the "lift" theory (not the mass theory) was they built a helicopter and flew it in the truck, and it did not create this magical "lift" to make the truck lighter.

But in the end, the myth wasn't testing the mass of a closed system and the effects of the birds resting/flying around in that closed system, it was testing the myth that the birds flying around affected the weight of the truck itself. Which it did not.

I guess I don't see the difference.

Yes, they did fly a helicopter to show that "flying" something inside a fixed volume doesn't change the weight.

 

[1100011CS]

Episode 77: Birds in a Truck
In "Birds in a Truck," Adam and Jamie tackle Sir Isaac Newton's founding principle of thermodynamics and the law of conservation of momentum. They're looking into a physics' classroom urban myth. If birds in a truck take flight do they lighten the load? Watch to see if the 'Busters will be outsmarted by a flock of pigeons ...

They don't really specify *how* the truck supposedly gets lighter. They're just testing the myth that the truck *would* get lighter (which it doesn't).

 

[jdoggivjc]

I guess I don't see the difference.

Yes, they did fly a helicopter to show that "flying" something inside a fixed volume doesn't change the weight.

The difference is they weren't testing the weight of the truck + the weight of the birds, then having the birds fly around and see if that made the weight of that closed system lighter. What they were testing was the weight of the truck itself and having the birds fly around and see if that made the truck itself lighter.

 

[CyinCo]

The difference is they weren't testing the weight of the truck + the weight of the birds, then having the birds fly around and see if that made the weight of that closed system lighter. What they were testing was the weight of the truck itself and having the birds fly around and see if that made the truck itself lighter.

OK. But really that is the same thing. Your baseline is just different.

 

[jdoggivjc]

OK. But really that is the same thing. Your baseline is just different.

The only reason why it appears to be the same thing is because the birds' weight is fairly negligible, being they weighed a couple of ounces. If the birds weighed 50-100 lbs, then it wouldn't be the same thing.

 

[clone52]

Take a look at isukendall's post. What I would like to know is that if the 2 buckets were connected by a tube, would you see the same weight change when you pour the water from the top bucket to the bottom bucket.

 

[SpokaneCY]

You change change your mass without "giving up" something. Standing on your hands would do nothing. Assume your body to be a control volume. If nothing leaves it, your mass hasn't changed. More likely, it was an inaccuracy of the scale.

If you're in an elevator and the cable snaps, will jumping up at the last second save your life?

 

[CYVADER]

Umm what? How does that change what you weigh? The best bet is to pee pee pee and pee, do anything you can to get as much waste out of your body as possible.

when you haven't drank more then 8 oz. of fluid for 2 straight days and have lost an average of 8 lbs a day in those 2 days, you really don't have much left to pee out or dooty. your best bet at this stage is to go outside and use the old finger down the throat trick. this usually works to get rid of the last couple pounds. if you start coughing up blood, you may want to consider moving up a weight class.