Vacuum Bazooka

What you need

1. Some BluTack to add a bit of weight.
2. A sheet of bubble wrap.
3. Parcel Tape.
4. Two long cardboard tubes (from wrapping paper).
5. A vacuum cleaner.

What you do

For the projectile:

1. Cut a strip of bubble wrap around 20 cm wide from your sheet. Make a small roll of BluTack, about 8 cm long and roll the bubble wrap around it. Make sure that the projectile just fits in your tube, trim if necessary, and then stick it together with parcel tape.

For the bazooka:

1. Cut one tube down to around 30 cm.

2. Cut a hole, no bigger than the size of the smaller tube, in the long tube around 10 / 15 cm from one end.

3. Cut curves in the end of the smaller tube so when placed over the hole there is a reasonably snug fit, with the two tubes forming a right angle.

4. Parcel tape the small tube over the hole in the longer tube.

5. Attach the vacuum cleaner to the bottom of the smaller tube with parcel tape (or another type of tape if you are worried about sticky residue).

6. With the projectile poised to fly from the back of the tube, switch the vacuum on and cover the front with a piece of cardboard.

7. Let go of the projectile and watch it fly!

What's going on

The vacuum removes most of the air from the cardboard tube since one end is sealed and the other is 'plugged' by the projectile. This means that there is very low pressure in the tube. Outside the tube, all around us and, critically, pushing on the end of the projectile is atmospheric pressure, the pressure exerted by the enormous amount of air sitting on top of us. It is this pressure that pushes the projectile along the tube. It gathers enough speed that it smashes through the card at the other end and flies off, hopefully hitting your target.

Special Safety Advice

The projectile is pretty fast moving so don't aim at people and don't use anything hard, sharp or breakable as a projectile!