It kind of goes without saying that making a screwdriver levitate for an extended period of time is no small feat, because those things are surprisingly heavy. So when YouTuber NightHawkInLight decided to test out an old mechanics trick - how to make a screwdriver float in mid-air using a low-powered air compressor - even he was skeptical. But never underestimate the possibilities when it comes to fluid dynamics, because as you can see in the video above, it totally works.

So what's going on here? The principle behind the trick is known as Bernoulli's principle, and it states that states that as the speed of a moving liquid or gas increases, the pressure within it decreases. So at first, the screwdriver is pushed away from the source of the compressed air, but because the air stream is travelling faster than the air surrounding it, the pocket of low pressure it creates results in a kind of vacuum that keeps it stuck in the air stream. Which means that rather than flying off into the distance - or into one of NightHawk's unprotected eyes - the screwdriver stays put, in mid-air, for as long as the compressed air is being funnelled through the machine.

It's the same principal that allows you to levitate ping pong balls over a hairdryer, without making them fly all over the room. Physics.org explains:

"The upward pressure from the hairdryer balances the downward force of gravity, keeping the ball 'levitating'. The more impressive part of this trick is being able to move the ball along with the hairdryer and angle it. The stream of air sticks to the surface of the ball - this is a demonstration of the Coanda Effect, which emerges when fluids like air or water pass over curved surfaces."

So as the air passes over the curved surface of a ping pong ball, it will wrap around it and move back out of the stream. This pushes the ball back into the stream for as long as their is constant airflow in this direction, even if the hairdryer is moved around.

Watch that trick below:

Thanks, fluid dynamics, for ensuring that no one lost an eye to a screwdriver today. We owe you one.

Source: Digg