Setting: Cooper, Olivia, and Hamza are hanging out in the library working on their homework.
Hamza: I never have the energy to do my homework.
Olivia: I keep telling you, Hammy, that’s an attitude problem, not an energy problem.
Hamza: I wish I had a machine to do all that work for me.
Cooper: If you had done your homework, you’d know what work machines really do. Hint: not homework.
Hamza: If you say so, Nerd Cooper. What is this “work” that machines do?
Olivia: I thought work was what energy did.
Hamza: (sarcastically) Is your name Nerd Cooper?
Cooper: Be nice. And she’s right. Work is when you change how something is moving: speed it up, slow it down, change its direction or how it's spinning—like when you kick a soccer ball.
Olivia: See Hamza, work can be fun!
Cooper: Basically it can be any movement that lines up with a push or pull. I mean that’s the science term “work.” But in everyday English we use the word “work” for a lot of different things.
Hamza: So, scientifically speaking, if I kick a ball and the ball knocks over a chair, I did the work of making the ball go, and then the ball did the work of knocking over the chair?
Olivia: I think so, Ham. You had energy from eating food, and then you exerted a force when you kicked the ball. Your kick gave energy to the ball, and the ball used the energy to knock over the chair.
Cooper: It’s cool to think about how something simple like kicking a ball has all these things going on.
Hamza: (daydreaming) I’m a machine on the soccer field.
Olivia: Well, they actually don’t allow machines on a soccer field, but they do in a hockey rink.
Hamza: You mean the Zamboni machine that smoothes the ice?
Cooper: Actually, she’s talking about the hockey stick.
Olivia: And you would know that if...
Hamza: I know! I know! If I did my homework. Wait, how is a stick a machine? It doesn’t take gas or electricity. That can’t be right.
Cooper: It is a machine! The way to figure it out is to think about whether it can transmit work.
Olivia: Coop, did you get the thing on the homework about pretending your pencil was a windshield wiper?
Hamza: What!? Oh great. Now I’m curious. I can’t believe I’m curious about homework. What have you two done to me?
Cooper: Here. Try it. Hold your pencil in front of you by the end and shift it back and forth like a windshield wiper. A small motion of your fingers causes a large motion at the other end of the pencil. That means it’s a machine. A lever to be exact.
Hamza: Oh, that’s kind of cool. I see the connection to the hockey stick. A player moves the stick at one end, but the stick moves a lot more at the other end and applies force to the puck so it goes faster than the hand moves. Wham!
Olivia: I guess golf and baseball are similar. They use levers. But I know people think of machines as things like cars or elevators. Not sticks.
Cooper: Well, it’s not that cars and elevators aren’t machines. They’re more like a bunch of machines put together into a complex machine. Look:
Cooper sketches a car and an elevator.