Challenge : Using only your breath, make a coin sitting near but not over the edge of a table rise and flip without touching it. FYI: I have been successful with a penny.
Yes, it can be done and it doesn’t take a hurricane wind. The secret is to blow a fast horizontal stream of air across the top of the coin.
YES! I said ACROSS THE TOP OF THE COIN.
CLUE: This moving air needs to be close but not touching the coin. Puckering you lips will produce the fastest stream of air and one that you direct across the top of the coin.
Before blowing across the coin, the air pressure above and below the coin is the same, thus the downward pressure of air on the to p of the coin is equal to the upward pressure of air on the bottom of the coin. As air increases in speed it exerts less pressure on the material that it flows across. This is known as the Bernoulli principle. The air moving across the top of the coin produces a low-pressure area above the coin as compared to the pressure of the air beneath the coin. This difference in the pressure lifts the coin and since the pressure on the upper surface is not the same over the entire surface, the coin will tend to flip over.
NEW CHALLENGE: I wonder…Can heavier coins be lifted?
|Physics For Every Kids|