My PBL Project

Principle:

The Bernoulli Effect underlies the principle of the aerofoil, by encouraging air to flow more quickly over the top surface of a wing an upward pressure is produced by the slower moving air beneath. It can also be demonstrated by holding up two sheets of paper and blowing between them, instead of moving apart, they are drawn together.

How Does it Work?

The upward pressure from the hairdryer balances the downward force of gravity, keeping the ball 'levitating'. The more impressive part of this trick – being able to move the ball along with the hairdryer and angle it and so on – is based on the Bernoulli principle. This states that fast moving fluids (including gases such as air) are at a lower pressure than slow moving fluids. So the air-stream from the hairdryer is at a much lower pressure than the air outside. A ball that is smaller than the diameter of the air stream can therefore be balanced within it – if the ball starts

Procedure:

1) Orient the hair dryer so that the outlet is pointing directly upwards, and turn it on.

2) Place a ball carefully in the flow from the hairdryer. It will balance in the air, appearing to levitate!

3)Gently move the hairdryer from side to side – the ball will stay in the air stream, i.e. will also move back and forth.

4) Repeat this process moving the hairdryer up and down.

5) Carefully tilt the hairdryer – the ball will still stay in the airstream, hanging in mid-air with nothing directly underneath it.

6) Then try using balls of differing sizes, and see how many they can be place in the air-stream all at once.

Safety Regulations:

Take precautions around electrical units

Wear heat protecting gloves if needed

Avoid directing heat in objects that have a possibility of damage or will be damaged, including humans.

Above all know your surrounding by being attentive and cautious.

'falling' out of the air-stream to one side then the higher pressure of the air outside the air-stream will push the ball back into the center. This is the process that enables the ball to balance inside the air stream and move around as the hairdryer is moved around.

Materials:

hair dryer (make sure you have an appropriate power supply available!)

small light balls (such as polystyrene balls available at most craft shops, or ping pong balls)

An electrical outlet

Plenty of space