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Space Shuttle Commander

Understanding Newton's Laws of Motion

Audience: Middle School Science Students

High above the earth in orbit......

Space Station Flight Controller: "Space Shuttle Columbia, you are clear for docking."
Shuttle Commander: "Roger that, Space Station Hopeful, we are coming in."
Shuttle Commander: "Easy as it goes. Reducing speed by firing forward thrusters."
Just then, a small piece of space debris rams into the shuttle!
Shuttle Commander: "Did you feel that! I think we've been hit by something. Space Station Hopeful, please report!"
Space Station Flight Controller: "I saw what happened, Columbia. A small object, about 2 feet square, hit your forward compartment. It just came out of nowhere. It looked like a tool box -- probably came from the construction activity going on in the Alpha section. I don't see any damage.
Shuttle Commander: "But it looks like the collision has nudged us out of position for the docking."
Space Station Flight Controller: "Yes, our sensors confirm that. You are about 6 inches off center. I suggest you abort the dock. If you are not accurate to within 1 centimeter, you will damage the docking station!"
Shuttle Commander: "Don't worry, I have it. Firing left thruster -- correcting trajectory."
Shuttle Commander: "Steady...... steady........I have it! Docking complete!"
Space Station Flight Controller: "Outstanding, Columbia. We'll meet you in the debriefing room."

The goal of this lesson

Did you ever wonder what it would feel like to be in outer space? The purpose of this lesson is to give you a first experience in a 'weightless' environment and to see if you can figure out how to control your movement through space! Sir Isaac Newton formulated 3 laws of motion that are still used by scientists and astronauts to predict and control the flight of their rockets.

At the end of this lesson, you should be able to:

Understanding the motion of objects

You probably take for granted that you and the things around you can move. However, scientists have tried to understand the motion of objects for thousands of years. One of the most brilliant scientists of all time was Isaac Newton who was born in England in 1642. Many of his ideas were built on the work of Galileo who, interestingly, died in 1642. Newton discovered many important laws of nature, but he is most famous for his 3 laws of motion.

Here is Newton's first law stated in everyday language:

"An object at rest tends to remain at rest and an object in motion tends to remain in motion unless acted upon by an outside force."

On one hand this law is easy to understand for objects that are not moving. A book sits on a table and obviously doesn't go anywhere. However, we tend to forget about the influence of many strong forces, such as friction and gravity. What do you think would happen if we could magically take away the forces of gravity and friction? According to Newton's first law, even a little push on the book would make it move forever.

Newton's second law describes how fast and in what direction objects will move if we give them pushes and tugs. Scientists have a special word to describe things like pushes, tugs, kicks, and nudges -- force. Here is Newton's second law also stated in everyday language:

"The speed and direction in which an object moves depends on the mass of the object and the amount of force that is applied to it and the direction of the force."

This second law is usually summarized by one of the most famous equations in all of science:

"Force equals mass times acceleration" or "F=ma" for short.

Examples of this law can be found everywhere. If you kick a soccer ball with a 'medium sized' kick, it will quickly roll across a field. But if you give the same size kick to a bowling ball, its initial speed will be much less. Of course, the friction of the both balls caused by their touching of the ground as they roll will result in both balls coming to a stop eventually. But remember Newton's first law. If there was no other forces acting on the balls, each would roll forever -- the soccer ball going fast and the bowling ball going slow.

Finally, here is Newton's third law:

"For every action, there is an equal and opposite reaction."

In other words, when you give something a push, it also pushes back. If you have ever fired a gun, you know that the "kick back" is a force to be reckoned with. Some forces act as impulses, or short bursts, such as kicking a soccer ball, hitting a baseball with a bat, or the "kick back" you feel when you fire a gun. Other forces are continuous, such as the wind produced by a ceiling fan, the push of a person behind a wheelbarrow, or the tug of gravity pulling a bicycle down a hill.

Newton's third law is especially important in helping to understand how machines like the Space Shuttle operate. But first, try to imagine yourself sitting in the middle of a frozen lake on a wagon while holding a shotgun. Every time you fire the gun, the kick back makes you move in the opposite direction. If there is little friction between the ice and the wagon's wheels, you will move very far before stopping. If you keeping firing the gun in the same direction, you move faster and faster. The only way to stop would be to turn around and fire the gun in exactly the opposite direction. The Space Shuttle is kind of like the wagon and its engines are kind of like the shot gun. But instead of an impulse force produced by the firing of a gun, the shuttle's engines provide continuous thrust.

And as my good friend Ron Zellner likes to say: "Action/Reaction ... it's not just a good idea, it's the law!"

Piloting the space shuttle

Here is a chance for you to feel what it would be like to be floating in outer space without having the forces of friction and gravity. This activity lets you pretend that you are the commander of the space shuttle -- the world's most complicated machine. In this activity, you will be able to go on a mission where you are trying to dock the shuttle with a space station, much like the mission dialogue at the top of this page.

It is best to play the simulation in pairs. As you take turns, help each try to find examples of Newton's first and second laws at work.

Click here to run the simulation.

Follow-up Activity

Here are some activities you might do next:

NASA Home Page
International Space Station
Space Shuttle Launch Schedule
Sir Isaac Newton

Copyright 1998 Lloyd Rieber

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