The slingshot car is an excellent introductory project to illustrate how potential energy is converted into kinetic energy, and the importance of low friction. Just be sure to watch your feet as cars go racing across the floor!
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Project Goal: Students build cars that are rapidly propelled across the floor at least 10 feet.
- Axle width
- Number of wheels
- Wheel Alignment means all the wheels all point in one direction
- Energy transformation is when one kind of energy turns into a different form
Prep: Bend paperclips into hooks (1 per student)
Safety: Launch cars only horizontally across the floor. Designate a launching area and direction when students begin to test.
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Step 1: Materials
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8 Craft sticks
Step 2: The Basic Frame
The frame can be just about any shape and size. I use a rectangular frame for my example because it has about the same proportions as a real car and it's easy to build.
Step 3: Adding Wheels
I like to use wheels that are at least as wide as one craft stick for stability.
You may need to give some hands-on help to students who are having trouble fitting a plastic wheel into a skewer. If it is being particularly stubborn, I will use my wood cutters to whittle the end of the skewer a little so that the wheel will fit easily.
Step 4: The Paperclip Hook
The hook is just like my Slingshot Rocket and Slingshot Dart Shooter. This little paperclip hook works very well for grabbing onto a rubberband, but also for releasing it at the right moment.
Children in grades 1-3 sometimes have difficulty bending the paperclips. You may want to bend these as part of your prep work.
The hook should be near the front of the car, though not necessarily in the exact position that's shown. If your students add some extensive modifications that interfere with the launching, you may need to relocate the hook.
Step 5: The Slingshot
These slingshots are easy to make and work well. Long rubber bands make launching easier, and it has a higher capacity for storing potential energy.
Step 6: Launching the Cars
- Place the car on a smooth, flat surface with the hook pointing in the direction that the car will be traveling.
- Hold the back of the car with one hands and the slingshot in the other.
- Hold the slingshot firmly with your thumb pressed against the stick. The rubber band should hang down from the stick and your hand should be in a 'thumbs-down' position.
- Drape the rubber band over the hook and begin pulling the car back until the band catches onto the hook.
- Pull back as much as you'd like while keeping the rubber band parallel with the floor. Release the car while keeping the stick pointing straight down.
Step 7: Safety, Tips and Troubleshooting
- CAUTION! This project can be dangerous. An inexperienced (or adventurous) user may fling the car into the air. Don't allow your students to fling the cars like this. Make sure that the rubber band stays parallel with the floor during the launch. It is natural for some students to whip the arm that is holding the slingshot upward at the moment of release. Correct them by making sure that they keep the slingshot pointing straight down during the launch. The energy should come from the rubber band, not from moving one's arm.
- Don't allow your students to add anything to their cars that might cause unnecessary harm, such as spiked skewers.
- Don't allow your students to fling the cars directly at each other.
- Some students will want to crash their cars into things. Bring plastic cups and stack them into pyramids to make some dramatic and appealing targets.
- Cars with a tall frame may interfere with the slingshot. You may need to adjust the placement of the hook in such cases.
- Some students have a difficult time launching their cars. Try to break down the launching procedure into simple steps: 1. Hold slingshot in front of you with the rubber band pointing down. 2. Hook the rubber band onto the car and pull back a lot. 3. Let go while keeping the slingshot pointing down.