# Does an hourglass weigh less while sand is falling?

I doubt that statement is entirely accurate either, sir.

It only works if the bottom of the ship is porous, but then you’ve got another problem.

It’s not that kind of ship

It’s an entirely different kind of sinking, altogether.

Correct. But if you were to mount it horizontally, and gently push on the pan, the balance will push the pan back to it original position. It will then measure the amount of force it is producing to maintain the original position.

Only tangentially related to the frogs-on-a-treadmill problem.

Just keep ‘em out of a pot of water if you plan on turning the burner on.

Speaking of which… what would happen if the hourglass were attached to a vertical treadmill?

You understood the reference!

Of course I do. It is a witticism, a gag, a bon mot, a fluctuation of words concluding with a trick ending.

But that’s not important now.

Let’s get this thread back on track.
I’m reading a Sean Carroll book now and it talks about hamiltonian mechanics (you google it if you want your brain to melt). He boils it down to NOT thinking about momentum (P) as M x V but as a fundamental property on its own and rewriting Newtons F=Ma as dP/dt = -dV/dx. Notice the negative sign. The balance between moving and not moving.

Note: V there is potential energy, not velocity.

I watch a lot of his videos. Some are understandable, some get deep fast. Smart cookie.

One thing I have learned from reading his books is an understanding of the Heisenberg Uncertainty Principle in terms I can understand. Take digital samples of an analog waveform and only look at one sample and you can’t know the frequency.

Yup. One thing that most layfolk don’t realize about the Uncertainty Principle is that it isn’t really a principle of quantum mechanics. It’s a principle of waves. All waves, from guitar strings to ocean surf to organ pipes. It’s just relevant to quantum mechanics because waves are a part of quantum mechanics.

Not that hard. Just start with a suitably large tank of water. Weigh that as your tare. Hold the animal submerged until it ceases moving. Weigh the result and subtract the tare. Done.

Oh you wanted to re-use the animal? Oops. Unless it a fish or similar.,)

I thought of that. Then, you gotta deal with loss of weight to the tank due to evaporation and struggle splashes.

Actually, the urine weight is often not trivial. I don’t weigh animals myself but, as I understand it, a lot of ‘natural weight loss’ can happen during the scary transfer to the weigh station.