Drag Racing Cups
Finish your coffee and use this fun and simple experiment to create an awesome racer!
What do Starbucks®, Dunkin’ Donuts®, and Einstein Bros® have in common? They all use disposable cups. What do these disposable cups have to do with SICK Science? They make awesome drag racers! In the Drag Racing Cups experiment, you’ll construct a simple and fun racer that converts potential energy into kinetic energy. Now if your parents would hurry up with their caramel macchiatos…
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- Two disposable coffee cups and lids
- Several rubber bands
- Plastic bead with hole ("pony" bead)
- Paper clip
- Small washer
- Pen or pencil
- Duct tape (or other strong tape)
On the bottom of both cups, trace the edge of a quarter with a pen or pencil. Try to keep the traced circle as centered on the bottom of the cups as possible.
Cut the traced circles out of the bottom of both cups using a pair of scissors.
Tape the cups together, bottom to bottom, using a strip of duct tape. The holes in the bottom should line up.
Poke a hole in the middle of each disposable lid using the pen or pencil. The hole shouldn’t be any wider than 5 mm.
Link several rubber bands together to make a chain that is close to the combined length of the cups. To link the rubber bands, lay two down with the ends overlapping. Then, pull the overlapped portion of the top rubber band around the bottom rubber band and up through the center hole. Pull them tight and the rubber bands should link together.
Run your rubber band chain through the middle of the cups.
Push one end of the rubber band chain through the hole in one disposable lid. Attach a paper clip to hold the rubber band in place and push the lid onto the cup.
Push the opposite end of your rubber band chain through the hole in the other lid and attach it to the cup.
Thread the rubber band through the middle of a small washer and then the bead. Put the straw through the end of the rubber band, just past the bead. Slide the straw through so that the rubber band is about 2 cm from one end of the straw.
Wind your racer by holding the cups in place and repeatedly spinning the straw around the bead.
Set the racer down and watch it go!
How Does It Work
When you twist the rubber band chain with the straw, you stretch the rubber band and wind it up. This winding and stretching creates and stores potential energy. Potential energy is energy that has the ability to do work in the future, but is not currently performing any work. The more twisting you apply to the rubber band, the more potential energy you create. When you put the Drag Racing Cups down on a surface, the rubber band unwinds and converts the potential energy into kinetic energy, the energy of a moving object, as it makes the cups roll.
Science Fair Connection
Creating Drag Racing Cups is pretty cool, but it isn’t a science fair project. You can create a science fair project by identifying a variable, or something that changes, in this experiment. Let’s take a look at some of the variable options that might work:
- Try testing different cup sizes. Which size rolls fastest? Which size rolls the farthest?
That’s just an idea, but you aren’t limited to that! Try coming up with different ideas of variables and give them a try. Remember, you can only change one thing at a time. If you are testing a different size of cup, make sure that the other factors are remaining the same.