Two more puzzles

[StefanS]

I'll add sg. as well, it's not really a puzzle, more a little physics problem:

You have an hourglass on a scale, displaying its weigth. Then you turn it around. What does the force over time diagram show?

No drawings are needed, just a small description will do it

 

[RussSchultz]

I'll add sg. as well, it's not really a puzzle, more a little physics problem:

You have an hourglass on a scale, displaying its weigth. Then you turn it around. What does the force over time diagram show?

No drawings are needed, just a small description will do it

It would weigh slightly less when 'ticking' as the sand in free fall is not in the equation

 

[nelg]

My wife gave me a similar puzzle to number two before.
Take one fuse and light both ends. At the same time take the second fuse and light one end. When the fuse that had both ends lighted burns out it will be 30 minutes. At this point light the other end of the second fuse. Having already burned for 30 minutes, having both ends lite it will burn for another 15 minutes. I hope the cake was chocolate.!

 

[StefanS]

Damn you're fast.

Here's another one:

How do you measure the amount of water in a chicken?

There're 2 solutions to this one...

 

[nelg]

Damn you're fast.

Here's another one:

How do you measure the amount of water in a chicken?

There're 2 solutions to this one...

Weigh it before and after my wife cooks it.

 

[StefanS]

Damn you're fast.

Here's another one:

How do you measure the amount of water in a chicken?

There're 2 solutions to this one...

Weigh it before and after my wife cooks it.

Well, that's the obvious solution, but it kills the chicken. Suppose you're an animal rights activist what would you do then?

 

[nelg]

Suppose you're an animal rights activist what would you do then?

Kill myself.

 

[MuFu]

Buy a monkey and treat it as you would your own child.

MuFu.

 

[Joe DeFuria]

Suppose you're an animal rights activist what would you do then?

Kill myself.

Lol!

 

[Simon F]

I'll add sg. as well, it's not really a puzzle, more a little physics problem:

You have an hourglass on a scale, displaying its weigth. Then you turn it around. What does the force over time diagram show?

No drawings are needed, just a small description will do it

It would weigh slightly less when 'ticking' as the sand in free fall is not in the equation

I'm a little confused by that answer. To clean up possible problems with the starting conditions, let's say there is a switch mechanism so that after we turn the hourglass over we can keep the sand in the upper container until we turn the switch. Now I can see that....

...for a short space of time, while the first few grains of sand fall, the weight will be temporarily lower BUT when they begin to hit the ground their kinetic energy and momentun (which was originally potential energy due to height) must be transfered in some manner to the scales. I haven't bothered to work out the exact equations but I suspect that the scales would then go ABOVE the original steady state reading. When the sand eventually runs out it will return

Or am I completely missing something?

 

[Bambers]

...for a short space of time, while the first few grains of sand fall, the weight will be temporarily lower BUT when they begin to hit the ground their kinetic energy and momentun (which was originally potential energy due to height) must be transfered in some manner to the scales. I haven't bothered to work out the exact equations but I suspect that the scales would then go ABOVE the original steady state reading. When the sand eventually runs out it will return

Or am I completely missing something?

i agree with that mostly except i'm not sure if it would go above the original value, I then thought that it would depend on height as more height would mean more momentum gained and more impulse when the sand strikes the bottom, then i realised that of course the more height the more sand will be in free fall at anyone time so in conclusion i think the weight will fall steadily while the sand is starting to free fall but then will rise sharply to some steady value which may be above or below the initial one depending on a bunch of factors. Anyone want to make a model of this?

 

[Simon F]

i agree with that mostly except i'm not sure if it would go above the original value, I then thought that it would depend on height as more height would mean more momentum gained and more impulse when the sand strikes the bottom, then i realised that of course the more height the more sand will be in free fall at anyone time so in conclusion i think the weight will fall steadily while the sand is starting to free fall but then will rise sharply to some steady value which may be above or below the initial one depending on a bunch of factors. Anyone want to make a model of this?

Oh enough of the micro text
I was also thinking that as the sand piles up, the micro impulses would go down.

Anyway, as simple thought experiment imagine yourself standing inside a tube on some scales with a big weight in each hand. Drop the first weight followed almost immediately by the second so that both will land (and settle) on the scales (but not your foot ).


Of course there is the "related" puzzle of the homing pigeons that have been loaded onto a plane. They get startled and start flying just as the plane is going to leave the ground. Does this make it easier, harder, or neither for the aeroplane to take off?

 

[Xmas]

Of course there is the "related" puzzle of the homing pigeons that have been loaded onto a plane. They get startled and start flying just as the plane is going to leave the ground. Does this make it easier, harder, or neither for the aeroplane to take off?

Depends on whether they push themselves off the plane to take off (then the answer is, harder) or just use their wings to ride on the airstream (in that case it depends on where they sit on the plane, and the answer could be all of them)
But realistically, the answer is: they don't matter

 

[StefanS]

Of course there is the "related" puzzle of the homing pigeons that have been loaded onto a plane. They get startled and start flying just as the plane is going to leave the ground. Does this make it easier, harder, or neither for the aeroplane to take off?

The pigeons are somewhat different; to fly they have to use their wings. This causes pressure to be applied to the surface of the plane which is exactly equal to their weight. Thus the answer is neither.

The sand however falls; the amount of the falling sand is therefore not measured by the scale; however at the end when the last bit of sand the weight goes back to normal. A simple sketch would look like this:
Sketch with typo
Please excuse the typo, was done in 10 seconds.
A mor complicated model would include a function of how the sand starts to roll / fall...
If you want to go microscopic: each sand particle is going to cause an oscillation of the spring in the scale...

Btw, anyone solved the chicken, without casualties?

 

[RussSchultz]

I think you would have some impulses as the sand hits the floor, though (I think) it would be minor as the instantaneous amount of sand hitting the floor would be pretty small, and the force generated would be pretty small, also.

 

[Xmas]

It depends on the height of the hourglass, the mass of the sand grains, and the scale (since you cannot really weigh an impulse).

 

[nelg]

I think you would have some impulses as the sand hits the floor, though (I think) it would be minor as the instantaneous amount of sand hitting the floor would be pretty small, and the force generated would be pretty small, also.

But lets not discount the effects of frequency.

 

[nelg]

Btw, anyone solved the chicken, without casualties?

Not that I know of but I think MuFu is adopting a monkey.

 

[StefanS]

It depends on the height of the hourglass, the mass of the sand grains, and the scale (since you cannot really weigh an impulse).

What happens is this: sand particle hits floor, thus force is exert on the spring in the scale; spring (if spring constant is small) starts oscillating; another sand particle hits at a random time; interference; another sand particle hits, ... -> statistically random oscillation around the lower value until no sand is dropped -----> scale displays true value again without oscillation...

 

[RussSchultz]

Btw, anyone solved the chicken, without casualties?

I can't think of a way to use Archimedes principles, unless we have a twin of the chicken than we can dessicate.

edit: or if we had a block of pure "chick-onium"