How Tall is Your Tower?. Emily Kogut Physics 240 Spring 2011. Jenny is happy. Her best friend Sam is coming to her house to play. They will do many things. Ding-dong. The doorbell rings. Jenny opens the door. “Hi Sam,” she says. “Hi Jenny!” Sam says.
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Sam puts moves his car so it is on top of Jenny’s car. “Three,” he counts.Jenny and Sam keep counting until the reach the top of Sam’s tower. “Four!” Sam says excitedly.
“My tower is four cars high,” says Sam. “Let’s measure your tower.”Jenny and Sam go to her tower. Jenny stands one doll next to the bottom of her tower. “One,” she counts.
Sam puts the other doll on top of Jenny’s doll. “Two,” he says. “And this is the top.”“Oh,” Jenny says sadly. “Well, Sam, you win. Your tower is four cars tall, but mine is only two dolls tall.”
“It was a fun contest,” Sam says, “but I think we should have a snack before we do it again.”“Yes,” Jenny says. She and Sam run to the kitchen.
Sam and Jenny are eating apples. Jenny’s older brother, Kevin, walks into the kitchen.“Your towers are cool,” he says. “Congratulations, Jenny.”
Jenny stares at Kevin. She can not believe her ears. “Me?” she asks. “But Sam’s tower is bigger.”“Yeah,” Sam adds. “We measured them with cars and dolls.”
Kevin nods understandingly. “Ah,” he says. “I’ll be right back!” He runs to his bedroom. When he comes back, he has something in his hand. “Follow me,” he says. Jenny and Sam follow Kevin to the playroom.
“This is a ruler,” Kevin explains. “We use it to measure things with a standard unit of measurement.”Sam frowns. “What does that mean?”
Kevin smiles. “It means that everyone can agree on its measurements. The ways of measuring with it are the same no matter where you are or what you are measuring.”
“Oh,” Jenny says. She smiles. “So you mean that ours were not the same because we measured my tower with dolls, but we measured Sam’s tower with cars.”
“Yes,” Kevin says. “Cars and dolls come in different sizes, so they are not standard. If I wanted to see whose tower was bigger using a racecar toy, I need to use the same racecar toy to measure both towers.”
“So?” Sam asks. “What’s wrong with that?”Kevin smiles. “What if everyone in your class built a tower? Or everyone in the school? It would take a long time to measure using only one racecar toy.”
“Then what can you use?” Sam asks.Kevin points to the numbers and lines on his ruler. “In science, we use the metric system. Each of these lines marks a centimeter. We use centimeters to measure small things, such as racecar toys, dolls, and towers.”
“Let’s try it!” Jenny exclaims.Kevin shows them how to hold the ruler. He places the bottom of the racecar next to the number zero on the ruler. “The number next to the top tells how tall the racecar is.”
“Eight,” reads Sam. “The car is eight centimeters tall.”“Now let’s measure my doll,” says Jenny. She takes the ruler from Kevin.“Make sure to start at zero,” says Kevin.
Jenny places the bottom of her doll’s foot next to the number zero on the ruler. She looks at the top of the doll’s head. “Twenty-five,” she reads. “The doll is twenty-five centimeters long.”
“Twenty-five is bigger than eight,” says Sam. “Your doll is bigger than my car.”Jenny nods. “Let’s measure our towers fairly, so we can really see who won!”
Jenny’s tower is fifty centimeters tall. Sam’s tower is thirty-two centimeters tall.“You win,” Sam says. He and Jenny shake hands.“Thanks for helping us, Kevin,” Jenny says.“You’re welcome,” Kevin says. He walks upstairs.
Jenny and Sam are going to measure things in their houses. You can do that, too! All you need is some measuring tape or a ruler. Remember to start at zero. You can keep track of your measurements here. Be sure to include the unit of measurement you used.
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