Alien in My Pocket #4 (8 page)

But what if, instead of jumping off a jungle gym, you slide down the fire pole. It's the same distance and the same direction. Instead you can reach the bottom without getting hurt. That's because your hands act like brakes. They slow you down as you go!

This is the idea we're going to employ in our own egg drop experiment. But we're going to do it a little differently. We're going to give that egg a set of brakes to slow it down. If we design it right, we can stop the egg the slow way so that it doesn't crack on impact.

Add brakes to avoid breaks!

 

For this experiment, you'll need:

• A yardstick, preferably the cheap kind made of wood

• A pair of pliers (not the needle-nosed kind)

• A few feet of string

• A drinking straw

• Strong tape

• A few rubber bands

• Some paperclips or wire

• A plastic cup

• Cardboard (a small-ish piece)

• A small tarp to help contain the mess if the egg breaks

• MOST IMPORTANT: An adult to help

 

1. Cut the piece of cardboard into a strip that's about an inch wide and two inches long. Fold it in half, and tape it onto the jaws of the pliers (the grabby part) to create a closed loop that can open and close a little bit. Make sure the tape is secure. The cardboard will be pinched by the pliers against the yardstick, creating brake pads that will slow the egg as it slides down the yardstick.

2. Cut two pieces off the drinking straw, each about 1″ long. Tape one piece to each end of the yardstick, both on the same edge. This will create the guide that helps make sure the egg drop brake system falls straight down.

3. Carefully poke a small hole in the cup below its rim. Thread the wire (could be a big paperclip) through the hole, and loop the end around the pivot of the pliers so that the cup can securely hang beneath the pliers. Give the wire a few twists around itself to help make sure it doesn't fall off either the pliers or the cup.

4. Open the pliers (spreading the closed loop of the jaws + cardboard) and loop the brake pads over the yardstick. Put a rubber band around the handles of the pliers, pulling them together. This should clamp the cardboard against the yardstick with a bit of a squeeze. Pick up the yardstick—do the pliers and cup hang in place on their own? If not, add another rubber band.

5. Put down a tarp that covers as much area as you can around the experiment site, in case your egg doesn't slow down enough and breaks!

6. Set up the guide string vertically by tying it to something a few feet off the ground. This might be the top of a table, a staircase banister, or even an upper hinge of a door in the house. Thread the string through the drinking straw guides on your yardstick, and tape the bottom end of the string to the tarp. Blue masking tape is a kind of tape that won't leave a residue.

Make the string a little bit tight so that the yardstick can slide up and down while the string guides it vertically.

If the string pulls the tarp up when you add tension, put something heavy on the end where the tape is. A brick should work well.

7. Pretest! Put something in the cup that weighs about as much as an egg. A rock might do, or a small beanbag. Position the pliers up at the top of the yardstick, and allow them to settle into a stable hanging position. Lift up the yardstick a little bit, and then drop it. When the yardstick hits the ground, the pliers should slide down the yardstick a little way, hopefully coming to a stop before the cup hits the ground, too. If everything held together OK, it's time for the real test!

8. Slide the pliers back to the top, and let them hang naturally with the cup below. Place the egg into the cup. Pick up the yardstick to your chosen height, cross your fingers, put on your safety glasses, and give a countdown. It's eggsperimentation time!
SPLAT
.

Questions to Ask

• Did the egg break?

• How far down the yardstick did the egg slide before it came to a stop?

• What happens when I add more rubber bands?

• What happens if I drop the yardstick from higher up?

• If I change the surface of the brake pads (for instance, by putting duct tape over the cardboard), does that change anything?

Troubleshooting

•
My egg hits the ground every time!
Try adding more rubber bands. If everything is set up right, but the egg still hits the ground, it might be that you need to squeeze harder on the brakes. You could also try dropping the yardstick from a lower height to begin with.

 

•
My egg keeps coming out of the cup!
You could add some tape to keep it in the cup. This experiment is designed to show the power of controlled deceleration in just one direction—downward. So if things are tippy and the egg is falling out, it's going to be harder to make good observations in the one direction you're interested in. Go ahead and do what's needed to keep it in place.

 

•
The yardstick comes off the string guides!
Add more tape.

More . . .

This is an experimental setup that can allow you to learn a lot of different things about what's going on! That's because it's relatively easy to repeat exactly the same conditions multiple times, allowing you to change small things and then very accurately record the differences. Try out lots of different combinations—different drop heights, different amounts of squeeze on the pads (adding or subtracting rubber bands), changing the brake pad material, and even seeing if you can slow down
two
eggs instead of one. What kinds of things do you observe with each change? What does that tell you about other things that you want to slow down, like a car, or a bus, or a bike, or yourself going down a slide or fire pole?

Have fun, and try not to make too big of a mess!

Excerpt from
Alien in My Pocket #5: Ohm vs. Amp

Read a sneak peek of book five of the Alien in My Pocket series:

OHM vs. AMP