Alien in My Pocket #5: Ohm vs. Amp (10 page)

Experiment Time

You'll probably have some success to start off with, but here are some ways you can work on the design and your own throwing motion to get the most out of your atlatl project.

       
1. Aim at different angles. Try throwing in a more upward direction. Does the ship fly in the path you expected? How might you adjust the angle you're throwing at so that it flies along the trajectory you want?

       
2. Try a different length of ship. It helps to have a longer ship, because it's harder for a long spaceship to tilt itself in a different course from the one you started throwing it in.

       
3. Test a different length of atlatl. If a long lever is good, is a longer lever better? Try a few different lengths of atlatl to see which gives you the most leverage. Do different atlatls require different techniques to throw effectively?

       
4. Try throwing at different speeds. An effective throw will combine raw power with good technique. You may want to experiment with a lower power throw that you can control better before adding additional throwing effort.

Safety Notes

       
•   Do this experiment with an adult! The adult isn't there to do the experiment for you, and in fact he or she should let you do as much of it as you can. But make sure someone is available to help with the hard parts, like cutting the cardboard and choosing a safe place to throw.

       
•   Choose a safe place to throw! It should be a wide-open area where there are no people, animals, or things that wouldn't like to get hit with a cardboard spaceship.

       
•   Start small! As with any experiment, don't ramp up to full power right away. Start with light, easy throws that let you get the hang of it and develop control first. Then ramp
up the power after you've developed some technique.

       
•   Make sure there is nothing in front of you that can get hit! If you read the prior instructions, you might notice this is mentioned twice. That's because this is really important! Even though your cardboard spaceship doesn't weigh very much and has a soft tip from the sponge you taped on, you should never throw it toward anybody.

Digging Deeper

To learn more about the science behind the atlatl you've built, look into the physics of projectile motion. The most important thing about the atlatl is that it's a clever method of getting even more benefit out of the thing our appendages have evolved to be good at: speed.

Your arm is really strong, and also really fast. The cardboard spaceship you're throwing doesn't weigh very much—so you can throw it very easily. But because it weighs so little, your body is actually not able to maximize the amount of energy
it can put into the projectile when throwing with just your normal arm. The atlatl enables your body to put more energy into the projectile by allowing you to bring it to an even higher release velocity (that means speed) than your hand can during a normal throw.

This can be illustrated by doing another experiment.

       
1. Hold the cardboard ship and prepare to throw it with just your hand. Have an adult hold your forearm steady and still, so you can only use your wrist to throw the ship. Your hand is functioning as the lever arm. Because the lever arm is so short, you won't be able to get the ship to a very high speed before you have to let go to throw it. The ship probably won't go very far.

       
2. Have the adult hold your upper arm steady while you throw. This way you're using your hand and forearm as the lever arm. Your lever arm is longer than last time. You'll be able to achieve a much higher speed than when you were throwing it with just your hand and wrist alone.

       
3. Throw it as you normally would, using the length of your hand, forearm, and upper arm. They become your lever arm and your shoulder joint becomes the fulcrum of this throwing lever. The ship should go pretty far!

       
4. Use your atlatl. The speed at the tip of the atlatl should be even higher than the speed you can make your hand go during a normal throw—meaning it'll go extra high in the air. It's that release velocity that matters, and you want it to be as high as possible. Maybe high enough to launch Ohm back into orbit. Be safe, and have fun!

“T
he answer is still no,” Zack said, stuffing a pair of jeans into the canvas bag that usually held his baseball gear.

“Just think about it,” Amp said from atop a pair of rolled-up wool socks that sat on Zack's desk.

“What part of ‘no' are you not getting?” Zack asked. “The
n
or the
o
part? It's really a pretty simple word.”

Amp stared off into space dreamily. “I've always wanted to go camping.” He sighed.

“What?” Zack said, fixing his eyes on his tiny
alien roommate. “Yesterday you had never even heard of camping! Now, suddenly, it's your lifelong goal? Give me a break, Short Pants.”

“We Erdians are fast learners,” Amp said with a proud shrug of his little blue shoulders. He folded his arms behind his head and nestled deeper into the sock. “Besides, what an adventure! The chance to battle the elements, the opportunity to encounter wild animals, the daily struggle to find food? Who would pass that up?”

“I already told you, we don't struggle to find food.” Zack groaned, pulling a fistful of underwear from an open drawer and tossing it into his bag. “We bring about five hundred pounds of food with us. We're not exactly hunting down beavers with bows and arrows.”

Amp sat up and grabbed his antennas with excitement. “And to sleep on the ground in that little cloth house held up by sticks.”

“You mean a tent,” Zack said flatly.

“Yes!” Amp said, snapping his fingers. “A tent! I want to sleep in a tent.”

“Forget it,” Zack said, sitting on the corner of his unmade bed and holding his head in his hands.
“Quit bugging me about this, okay? You know my family can never know you're here. They'd freak out if they ever saw you. Call the park ranger. Call the cops. Call the government. Not to mention you've still got a little alien invasion to stop. Remember the whole reason you came to this planet in the first place? You don't want the Erdian Army to arrive only to find their lead scout napping in the woods.”

“Come on, a camping trip might be just the thing I need to get the creative juices flowing again.”

“It's too risky. If anyone else sees you, they'll take you away and dissect you like a frog.”

“But look at the size of me,” Amp said, standing up and doing a sort of jumping-jack motion. “I'm so little, they'd never see me. Plus, you know how good I am at staying out of sight.”

Zack looked over at Amp and shook his head at his friend's energy.

His family had gone on an annual camping trip for the last three years, and each year had been a disaster. The McGee family just wasn't the outdoorsy type. But every year Zack's dad insisted they go. And every year, a perfectly good
three-day weekend was ruined.

Amp fell onto his belly and pressed his face into the fluffy socks. “I promise if you take me with you to the Crooked Forest,” his muffled voice begged, “you'll never know I was even there. I'll be like a ninja.”

“It's not called the Crooked Forest,” Zack said, rolling his eyes. “It's called Twisted Grove State Park.”

“Yes! That's it. I want to see the ghost, too,” Amp said, rolling onto his back and staring up at the ceiling. “I've never seen a ghost.”

“There's no ghost,” Zack sighed. “That's just a story people made up.”

“You told me the outlaw Nasty Ned hid his stolen gold in that forest over a hundred years ago, but could never find the spot where he buried it. Now his ghost wanders through the trees at night trying to find it.”

“I was just reading you that stuff from the back of the park's map,” Zack explained.

Amp sat up. “The anger from Nasty Ned's ghost made all those trees crooked. That's just so exciting.”

“But it's not true! It's just something they wrote to make the campgrounds sound mysterious to tourists. It's just a bunch of trees that got bent out of shape. It's no big deal.”

“Watch this,” Amp said, and he disappeared from sight. “See, nobody will see me,” his voice explained. “I'll be invisible. Now let's go hug some trees and see ghosts in the Crooked Forest!”

Zack pinched the bridge of his nose in frustration.

He knew all too well about the Erdian mind trick that enabled Amp to stop your brain from seeing him. The way Amp explained it, he could make your brain forget you were seeing him at the same instant you were seeing him. Zack had trained himself to block the mind trick when he wanted to, but now he just stared at the empty space above the sock.

“Forget it,” Zack said, yanking the sock off the desk and stuffing it in his bag. He heard Amp give an invisible cry and then appear just as he crashed onto the desk.

“Ouch!” Amp yelled. “That was incredibly rude.”

“See, you can't always be invisible,” Zack said
with a chuckle, zipping up his bag and heading toward the door. “Under the bed are enough Ritz Crackers and SweeTarts to last you a month. I'll be back late on Monday night, okay? Are we good?”

“But I'll be so bored,” Amp whined, rubbing the back of his head.

“Just stay in here and out of trouble,” Zack said and closed his door.

Alone in the hallway, Zack pressed on the door to make sure it was securely shut, sighed, shook his head, and headed downstairs.

There was one more thing he had to do before leaving.

The Ol' Switcheroo

“J
immy has pinkeye,” Zack's little brother, Taylor, reported when Zack dropped his bag at the front door. “He can't go camping with us.”

“No biggie,” Zack said. “More room in the kids' tent.”

“But Jimmy always comes with us,” Taylor moaned. “He just called. Both his eyes are glued shut with pus.”

“Gross! Thanks for sharing, Taylor,” Zack said.

Taylor sighed. “This will be our worst camping trip ever.”

Zack shrugged. “I'm not so sure. The bar is set pretty low.”

“Oh, stop it, you two,” Zack's mom said, rolling out a plastic cooler stuffed with ice and food. “C'mon, Zack, bring this and your bag out to Dad.
Olivia is helping him put everything on top of the car.”

“Olivia? Why?” Zack asked.

Helping Dad tie down the tents and bags was usually his job. And while Olivia was his best friend and next-door neighbor, sometimes she helped out around his house a little too often, which tended to make him look lazy by comparison.

Mom brushed Zack's hair from his face with her fingers. “Since Jimmy couldn't go with us, I asked Olivia to come instead. It'll be so fun.”

Zack pulled away from his mom. “What?!”

Zack had planned on having Olivia keep an eye on Amp while he was gone. She was the only other person on the planet who knew about Amp, so her going on this trip threw a major wrench into his plans.

Plus, when Zack thought about the close quarters of a tent, camping with Olivia might be a little . . . embarrassing. He flapped his arms, trying to think of something to say. “Mom, I can't sleep in a tent with Olivia. She's a girl. It's just weird!”

“Yeah, Zack likes to fart when he camps,”
Taylor said. “Nobody should be subjected to his weaponized toots.”

“Don't be crude, honey,” Mom said to Taylor with a tsk-tsk. “Zack can't help it if he has a sensitive system.”

“I don't have a sensitive system,” Zack said. “It's just that . . . I don't know. It's just weird, Mom.”

What Zack couldn't say was that, while he knew Olivia would make this camping trip a lot more fun, the thought of leaving Amp unsupervised for a whole three-day weekend made him nervous. Amp was like a disaster magnet.

“Zack also likes to sleep in his underwear,” Taylor said. “Now he can't.”

“That's not true,” Zack said.

Mom continued to try to fix up Zack's hair. “Olivia and I can sleep in the small tent, and you, Taylor, and your father can sleep in the big tent.”

“Dad! He snores like a volcano,” Zack protested.

“Volcanoes don't snore,” Taylor said, shaking his head at his brother's lack of basic science knowledge. “But they do sort of burp. Mostly
water vapor and carbon dioxide. But also lots of different sulfur compounds. It's a long list and varies by volcano.”

Zack stared at his brother like he was the alien in the house, and then began flapping his arms again. “It's bad enough that Taylor laughs in his sleep, now I get snoring on top of it?”

“I don't laugh in my sleep!” Taylor shouted, apparently insulted at being accused of sleep-laughing.

“She's already coming,” Mom said with a firm nod. “Now let's have fun, you two.”

Zack looked out the window and could see Olivia on top of the car, helping Zack's dad thread twine through the handles of various suitcases and tent bags.

Olivia
was
also going to feed Mr. Jinxy and walk Smokey while they were gone. Now somebody else would have to come into the house to take care of the cat and the dog, further risking the accidental discovery of Amp.

Zack closed his eyes and shook his head slowly. Camping had always seemed inconvenient, but this year there was so much more at stake.

Zack had a bad feeling about this trip.

He wished he were the one who had come down with pinkeye.

But he was not the lucky type.