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DIY Marshmallow Bazooka

National Office

Keen to do some science at home to get in the mood for National Science Week? This project, courtesy of Dr Graham Walker (@DrGrahams), could be just the thing!

Graham will be performing his Extraordinary Science with Ordinary Stuff shows all over the ACT and regional NSW for National Science Week – check them out on the website.

For the full Extraordinary Science with Ordinary Stuff activity book and competition visit http://scienceshowoffs.net/blog/activities/.

This Inspiring Australia initiative is supported by the Australian Government as part of National Science Week.

DIY Marshmallow Bazooka

CAUTION: Take care when cutting the pipe. The marshmallows fly fast so don’t shoot them at anything fragile or people. If you must shoot them at people – which we don’t suggest – make sure they are wearing eye protection.

Materials:

What to do:

  1. Cut about 20 cm off the end of the PVC tube. Attach the pipe joiner to one end, and the bottom of the ‘T’ in the T-junction to the other end.
  2. Use the pipe joiner to attach the vacuum cleaner – most vacuums fit nicely but if not use some tape to get a good seal.
  3. Marshmallow bazookaAttach the long remaining piece of the PVC tube to one of the sides of the T-junction (the picture below shows how the pieces fit together
  4. Turn the vacuum on. Hold the paper/plastic square – henceforth called the ‘cap’ – to the open side of the ‘T’. The cap should get pushed (‘sucked’) onto the opening and held in place.
  5. Make sure you’re aiming into a clear open space. The marshmallow will fly out the opening where the cap is.
  6. To fire, put the marshmallow in the end of the long tube – you may need a helper to hold or load the bazooka. It should shoot out the other end, knocking the cap off.

ATTENTION THRILL SEEKERS: Can you design a cap that stays on and resets with each launch? Hint: a hinging cap could be one answer. Solved it? Behold the fully automatic marshmallow bazooka!

What’s happening?

The vacuum cleaner creates lower pressure inside the vacuum than outside, which is at normal atmospheric pressure.  Atmospheric pressure is the weight of the air in the atmosphere pushing – all the air all the way up to space is stacked on top of us and it weighs a lot! While people say the vacuum sucks air in, the truth is that the higher atmospheric pressure outside actually pushes air in.

The set up of tubes and the cap allows us to place the marshmallow in the way of this moving air, which applies a force and pushes (‘sucks’) the projectile along the tube and launches it out. The projectile has kinetic or moving energy.

While the air is being pushed (‘sucked’) into the vacuum and turns 90 degrees down the T-junction, the marshmallow continues to go in the same direction. Once the marshmallow is going fast one way, it continues to go that way and flies out the end, knocking the cap off. This is an example of Newton’s 1st law – an object in motion continues in motion until another force changes that.