Have you ever seen one of those roller coasters that shoots out of the station at an insanely high speed? These roller coasters don’t need to climb hills first to use gravitational potential energy—their power comes from magnetism and energy conservation.
A series of electromagnets (magnets made by pumping electrical current through coils of wire) alternately push and pull on the rollercoaster, pumping up its speed pretty quickly. Some engineers have imagined using the same idea to launch objects into space (from, say, a base on the Moon) without using rockets.
In this project, you’re going to build a very simple magnetic accelerator to launch steel balls at targets. What could possibly go wrong?
Problem
Build a simple magnetic linear accelerator.
Materials
Procedure
Results
The ball will be attracted to the first magnet and set off a chain reaction of balls firing between the magnets until the last one flies off the ruler at high speed to strike its target.
Why?
What you just saw is a fantastic example of energy conservation. Energy from one ball gets transferred to the next, and then to the next, and so on. But where is all the energy in the last ball coming from if the first ball starts off from rest?
The answer is in the magnets.
Before the starting ball is released, there is potential energy stored up between the ball and the first magnet. The magnet and ball feel an attractive force, but your finger is preventing anything from happening. Once you let go of the ball, it gets drawn towards the magnet (which won’t move because it’s taped down). Potential energy gets converted to kinetic energy—the energy of motion. This is no different then holding a ball in the air and letting it go.
Eventually the ball strikes the magnet—but where does all that energy go? Well, it gets transferred to the balls on the other side of the magnet. The ball closest to the magnet is held pretty tight, but the second ball is farther away and doesn’t feel as strong an attraction to the magnet. This means there’s enough kinetic energy from the first ball to send this ball flying off with nearly the same amount of energy. (That’s why we need two balls stuck to the other side of the magnet: to lessen the attractive force a bit. Try getting it to work with only one ball loaded up next to each magnet and see what happens.)
This second ball is launched at roughly the same velocity as the first ball achieved. As this second ball gets drawn to the second magnet, the attractive force causes it to accelerate and hit the second magnet at a higher velocity than the first ball hit the first magnet. The third ball takes off with the highest velocity achieved by the second ball, and since it gets accelerated by the third magnet in turn, it strikes third magnet faster and harder than the first two balls struck their respective magnets.
Are you seeing a pattern begin to emerge? With each added magnet, more kinetic energy accumulates in each launched ball. The last ball takes off with the combined kinetic energies of all the balls that came before it!
In principle, you can add more rulers and magnets and get the final ball moving as fast as you like—up to a point. Eventually, the balls would be moving fast enough to break the magnets, a limit for which I’m sure your target is very thankful.
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Education.com provides the Science Fair Project Ideas for informational purposes only. Education.com does not make any guarantee or representation regarding the Science Fair Project Ideas and is not responsible or liable for any loss or damage, directly or indirectly, caused by your use of such information. By accessing the Science Fair Project Ideas, you waive and renounce any claims against Education.com that arise thereof. In addition, your access to Education.com's website and Science Fair Project Ideas is covered by Education.com's Privacy Policy and site Terms of Use, which include limitations on Education.com's liability.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state's handbook of Science Safety.
