Here's a puzzle for you.

[Swanny]

Galileo pointed out that, ignoring air resistance, all bodies fall with the same acceleration. But what about objects sinking in water of different temperatures? Here is the puzzle: Suppose you drop a brick in each of two identical tanks. One of the tanks has water at 40 degrees F and the other has it at 30 degrees F. Which brick would sink faster?

:-?

[NiteW4tcher]

i have a headache ;D

[kn]

The one in the tank with 40 degree water.

[bobf279]

the colder water would be denser

[Scotty]

Duuuh! Water freezes at 32ºF (for the luddites who still use stone age units), so 30ºF is below freezing.... ::) ::) ::) A brick isn't going to sink very quickly through ice is it...?

The density of water remains pretty much the same between 1ºC and 99ºC, reducing a bit when it reaches solid phase (freezes), and substantially more when it reaches the gas phase (steam).

[@bj]

You haven't said anything about pressure - so - assuming a smidge above sea level...

30 F = -1 C

In other words ice. The brick will not sink - but sit on top the ice - assuming the water hasn't been super distilled - in which case - under certain circumstances - the water won't turn to ice...

40 F = 4 C

Assuming the above mentioned pressure caviats etc - water is liquid at this temperature - therefore the brick will sink.

Interesting to note however - that at 4C specifically - water reaches its highest density... higher than water at 3C or 5C

Or put another way - the brick will sink faster at 3C or 5C than at 4C

[Jon_W]

Assumng that the tanks are open to atnosphere at sea level and are pure water:

Scotty is right. The water in the lower tank would be frozen!


Here is a headache inducing one:

If you drop two identicle dimension spheres, with the same surface finish and dropped from the same height. One shhere is of a heavy material (say iron) the other of a light material (say wood).

Experement has shown that the wooden one will hit the ground first.

Why??

[b_m1957]

Here is a headache inducing one:

If you drop two identicle dimension spheres, with the same surface finish and dropped from the same height. One shhere is of a heavy material (say iron) the other of a light material (say wood).

Experement has shown that the wooden one will hit the ground first.

Why??

I'm struggling.

The full force formula applied to all 3 pairs of bodies gives a net acceleration of the Earth (in 1/r^2) biased towards the heavy ball. The force between the balls give a component to each of them in the direction of Earth (in 1/r^4), biased to the light ball.

Without more detailed analysis (and detail on the setup) seems to me the 1/r^2 would trump the 1/r^4 and the heavy ball would touch down first!

[Loops]

Assumng that the tanks are open to atnosphere at sea level and are pure water:

Scotty is right. The water in the lower tank would be frozen!


Here is a headache inducing one:

If you drop two identicle dimension spheres, with the same surface finish and dropped from the same height. One shhere is of a heavy material (say iron) the other of a light material (say wood).

Experement has shown that the wooden one will hit the ground first.

Why??

You attached the iron one to a bungee cord? :-/

[bobf279]

dropped at the same time?

oh and water at 30F is definitely denser as ice is frozen water

[Scotty]

oh and water at 30F is definitely denser as ice is frozen water
Were that the case, it would have been the iceberg that sank, not the Titanic. Ice floats in water because it has a lower density than water... It is more solid, but has a lower density :)

[Jon_W]

Here is a headache inducing one:

If you drop two identicle dimension spheres, with the same surface finish and dropped from the same height. One shhere is of a heavy material (say iron) the other of a light material (say wood).

Experement has shown that the wooden one will hit the ground first.

Why??

I'm struggling.

The full force formula applied to all 3 pairs of bodies gives a net acceleration of the Earth (in 1/r^2) biased towards the heavy ball. The force between the balls give a component to each of them in the direction of Earth (in 1/r^4), biased to the light ball.

Without more detailed analysis (and detail on the setup) seems to me the 1/r^2 would trump the 1/r^4 and the heavy ball would touch down first!

You and every other scientist. The pheonmonon was forst recorded by the ancient greeks and has remained a mystery ever since.

Here's another.

http://en.wikipedia.org/wiki/Riemann_hypothesis

The Reimann Hypothesis. Simple question, prove whether it is true or False.

The Prize: At least $1m, Probably the Nobel Prize for Mathematics plus many more accolades.

[Col]

OK hands up all those who understood The Reimann Hypothesis :-? :-? :P

[Jon_W]

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