Today, I went as a volunteer to judge in Special Awards Category to the Silicon Valley Science and Technology championship in San Jose. Its the biggest Science Fair I have attended so far. It was just so awesome. The caliber of projects that students put together was just mind blowing. The fair was for 6-12th grades and I was looking mostly at 6th and 7th grade projects.
Saw quite a few projects even at 6th grade level on solar and Wind Power. And quite a few on day today issues we face all around us...
Now for the answer to the previous question - How to blow warm air or cold air from our mouths...
If you blow with an open mouth slowly on your hand, it feels warm but if you blow with your lips closer (a narrow band of air), it feels cold.
The reason for the same air to feel warm or cold has to do with mixing with the air once it comes out of the mouth. When you blow with an open mouth, a wider jet of air comes out and it doesnt mix with the outside air nearly as quickly and it still feels warm (temperature of the air coming out of our lungs). But when you blow with pursed lips, the jet of air is narrow and the air tends to mix with the air around it and feels cooler. If you blow air with pursed lips but your hand is very close to mouth, the air does feel warm as it doesnt get mixed with outside air quick enough...
till the next science question...
Good night
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