Parents, Educators & Engineers

# Kicking Machine

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Build a machine that kicks a Ping-Pong ball into a cup lying on its side 12 inches away. Use either (1) a pendulum, (2) a rubber band, or (3) a combination of the two to do this.

## MATERIALS*

• Balls (Ping-Pong and golf)
• Corrugated cardboard
• Paper clips
• Paper cups
• Popsicle sticks
• Rubber bands
• Ruler
• Scissors
• String
• Tape (masking or duct)
• Thin metal wire (optional)
• Wooden skewers

* For information on where to get these materials, see page 6 or visit pbskidsgo.org../engineers.

## BRAINSTORM AND DESIGN

Before you begin designing your machine, brainstorm answers to the following questions. Record and sketch your ideas in your design notebook.

• Will my machine use a pendulum or rubber band (or a combination) to send a ball into the cup?
• How will I stop the machine from launching the ball before I'm ready to release it?
• How will the machine be triggered when I'm ready to launch the ball?
• How will I make sure the pendulum or rubber band launches the ball straight enough and with the right amount of force so it goes into the cup?

Think about how to create different release points for the pendulum or rubber band so you have more control over a launched ball. Also consider how to determine the right amount of energy to store up before making your shot.

## BUILD, TEST, AND REDESIGN

When you lift a pendulum or stretch a rubber band, you increase its potential energy. Potential energy is energy that is stored. When you release the pendulum or rubber band, its potential energy is turned into kinetic energy, the energy of motion. Many machines have this in commonâ€”they turn potential energy (e.g., fuel, electricity, muscle power, springs, or weights) into kinetic energy that can be used to do a task (in this case, launch a ball).

Once you've built your machine, test it. Lay a cup on its side 12 inches away and see if you can get the ball in. When we made our machine, we had to debug some problems. For example, the ball bumped into parts of our machine and went in unexpected directions, and the stretched rubber band bent our frame. It was also hard to get the pendulum and rubber band to stay pulled back. If things like this happen to you, figure out a way to fix the problem so that your machine works every time.