Is it because the velocity of one water molecule relative to the other water molecules is low? When I stick my hand into a cold stream, why do I feel that it’s cold even though the water is moving fast into my hand? Shouldn’t the water flowing fast mean more collisions with my hand (which I thought is how we sensed temperature)?
In: Physics
The fastest estimate of the speed of a river is 3.1 m/s.
One liter (=1 kilogram) of water with this speed has a kinetic energy of 4.805 joules, being that it has 1kg mass and the kinetic energy equation is 1/2 m v^(2).
This amount of kinetic energy were it converted purely to heat energy, as an airplane’s brakes do, could hope to improve the temperature of one kilogram (=1 liter) of water by 0.0011 degrees Celsius. For you see, it takes 1 calories (not Calories, but calories) to raise one gram of water by 1 degree Celsius, and it takes 1000 calories to raise 1000 grams of water by 1 degree Celsius. And 1000 calories is 4184 joules. Easy division.
This is not a lot at all, and though this kinetic energy does constantly convert into the water’s temperature energy, it does not do so fast enough to make it “hot” by a typical human measure.
Latest Answers