Old but fun video

[HerrSticks]

While some may cite this as a reason to increase laser restrictions, I however would disagree.

This video, (i bet most of you may have seen it) is clearly shot in a lab, with and by technician who work with this laser daily and im sure are well aware of the risks and safety precautions.

Damn that laser gets bright, all it is a laser being shot into a mug filled with coffe in an attempt to heat it.

It looks like some lit a magnesium strip and dropped it in the mug, it gets REALLY bright, had i been in that room chances i would have turned around or put on some welding goggles.

Two-killowatt laser heats coffee, wows onlookers -- Engadget

 

[Elektrotechniker]

Is it healthy to drink that ?

 

[Cyparagon]

No. The laser light will hide in the coffee... biding its time. Then it will jump from the coffee to your face when you bring the cup to your lips to drink. Also, the laser radiation will cause the water molecules to get cancer and then they'll turn your loved ones into zombies out of spite. That's why you should always wear three boots when paddling your doghouse down hill in any attempt to make a grasshopper eat your rancid pancakes at any time besides 8:23 PM unless you can pay for a 24-bit eggplant.

 

[HerrSticks]

if you watch carefully you can see the coffee being brought to a boil before they are rotated out.
From the time the laser hits the cup and it begins to boil and is rotated out is 20 seconds.
They look like they are oversize mugs, which usually hold about 1.5 to 2 cups, and they seem to be about half full so im guessing its about 1cup of water heated to a boil in 20 seconds.

With that laser just think how fast my ramen and macaroni would be done!

 

[Cyparagon]

Some math just for fun:

20 seconds at 2kW is 40kJ. The heat equation is something like Q=mc∆T where Q is the heat change in heat energy, m is mass, c is the specific heat of the material, and ∆T is the change in temperature. Mass would be about 250g for a cup, and the specific heat of water is 4.186. I get 40,000=4.186*250*(100-x) where x is the initial temperature in C. Assuming 100% absorption, the water had to have started at 62C or 143F.

 

[ped]

^^ was just gonna say the same thing


No really...i was

 

[anselm]

Mass would be about 250g for a cup, and the specific heat of water is 4.186. I get 40,000=4.186*250*(100-x) where x is the initial temperature in C

Now you've gotten me all confused:
SI unit for mass is the kilogram, not the gram. But then results don't make any sense no more....:thinking:
Darn.

 

[TeLight]

Cyparagon's initial calculation is correct because the specific heat constant for water has units joule/gram °C. Therefore the 4.186 constant can only be used to calculate specific heats of water in gram amounts.