Rev. 2/1/2006
Newton’s First Law: Experimenting with Inertia!
Science Concepts:
Newton’s First Law of motion tells us that a body at rest will remain at rest unless acted upon by a net force. It also states that a body in motion will maintain that motion, in the same direction and with the same speed unless acted upon by an unbalanced force.
Duration:
30 minutes
Essential Questions:
What are the properties of inertia?
How do we commonly experience inertia?
About this Poster
The Swift Gamma-Ray Burst Explorer is a NASA mission which is observing the highest energy explosions in the Universe–gamma-ray bursts (GRBs). Launched in November, 2004, Swift is detecting and observing hundreds of these explosions, vastly increasing scientists’ knowledge of these enigmatic events. Education and public outreach (E/PO) is also one of the goals of the mission. The NASA E/PO Group at Sonoma State University develops classroom activities inspired by the science and technology of the Swift mission, and which are aligned with the National Science Education Standards. This poster and activity are part of a set of four educational wallsheets which are aimed at grades 6-8, and which can be displayed as a set or separately in the classroom. The front of the poster illustrates Newton’s First Law (EXPLAIN HOW). For Aurore: can we add instead a person’s hand hitting an upside down ketchup bottle and a person in a car with a seatbelt on coming to a sudden stop and their head going forward? Or how about a person riding a skateboard which hits something and the person falls off?
The activity below provides a simple illustration of Newton’s First Law. The activity is complete and ready to use in your classroom; the only extra materials you need are a smooth-covered book, a book with a rough cover, a glossy book cover or smooth large sheet of paper, assorted small objects to place on top of the book. The activity is designed and laid out so that you can easily make copies of the student worksheet and the other handouts.
The NASA E/PO Group at Sonoma State University:
• Prof. Lynn Cominsky: Project Director
• Dr. Phil Plait: Education Resource Director
• Sarah Silva: Program Manager
• Tim Graves: Information Technology Consultant
• Aurore Simonnet: Scientific Illustrator
We gratefully acknowledge the advice and assistance of the NASA Astrophysics division Educator
Ambassador (EA) team, with extra thanks to EAs Dr. Tom Arnold, Bruce Hemp, Rae McEntyre, and Rob Sparks and to Dr. Kevin McLin. This poster set represents an extensive revision of the materials originally created by Dr. Laura Whitlock and Kara Granger for the Swift E/PO program. The Swift Education and Public Outreach website is http://swift.sonoma.edu. This poster and other Swift educational materials can be found at: http://swift.sonoma.edu/education/
Background information:
Sir Isaac Newton (1642-1727) established the scientific laws that govern 99% or more of our everyday experiences – from how the Moon orbits the Earth and the planets orbit the Sun to how a hockey puck slides over ice, a person rides a bicycle, or a rocket launches a satellite into space. Newton’s Laws are considered by many to be the most important laws of all physical science. They are also a great way to introduce students to the concepts, applications, vocabulary, and methods of science.
Newton’s Laws are related to the concept of motion: Why does an object move like it does? How does the object accelerate or decelerate? To understand these things, we need to understand the relationship between force and motion.
Forces can cause motion. But what exactly is a force? We can think of a force as a push or a pull. A force has a direction as well as a magnitude: in other words, force is a vector quantity. In a diagram, a force can be represented by an arrow indicating its two qualities: The direction of the arrow shows the direction of the force (push or pull). The length of the arrow is proportional to the magnitude (or strength) of the force.
Historical Perspective
Built upon foundations laid primarily by Aristotle and Galileo, Sir Isaac Newton’s First Law of Motion explains the connection between force and motion.
Aristotle theorized that a force is required to keep an object in motion. He believed that the greater the force was on a body, the greater the speed of that body. His theory was widely accepted, since it basically agreed with life’s everyday experiences. Aristotle’s theory remained largely undisputed for almost 2000 years, when Galileo came to a different conclusion.
Galileo believed that it was just as natural for a body to be in horizontal motion at a constant speed as it was for it to be at rest. Galileo first had to imagine a “perfect world” – one without friction – in which such a conclusion would be true.
Isaac Newton built upon Galileo’s ideas. In his work known as the “Principia,” published in 1687, Newton readily acknowledged his debt to Galileo. His First Law of Motion stated: A body continues at rest or in motion in a straight line with a constant speed until acted on by a non-zero net force. The tendency of a body to maintain its status quo is called inertia. Newton’s First Law is often referred to as the Law of Inertia.
Newton’s Laws apply to macroscopic systems – things you can feel and see. There are environments for which Newton’s Laws (or Classical Mechanics) only provide an approximate answer, and more general physical laws must be used. For example, black holes and objects moving at nearly the speed of light are more accurately explained by General Relativity, while subatomic particles are explained by Quantum Mechanics.
Newton’s First Law and the Swift Satellite
On November 20, 2004, the Swift satellite was sealed in the nosecone of a Delta 2 rocket, ready for launch from Cape Canaveral, Florida. Immediately prior to launch, Swift was “an object at rest” and so was the rocket. There was no net force on Swift or the rocket, and so both of them remained at rest. When ignition of the solid rocket boosters occurred, at XXX (time), a net force began to be applied to the rocket. Shortly thereafter, the rocket began to move upwards, in a straight line at YYY km/sec. You can see the Swift launch in a video at: http://www.nasa.gov/mission_pages/swift/multimedia/index.html
(Phil, please put in some stuff about how much mass the entire thing had, how much fuel it took).
Materials: [lay this out to be like the other activities, in a bulleted list for each thing]
• one bookcover or large piece of smooth paper
• one book with a hard, glossy cover
• one book with a rough or non-glossy cover
• objects to place on the bookcover
Objectives: Students will…
Students will notice that an object at rest tends to stay at rest, if frictional effects are minimal.
Students will see that increases in friction cause violations of Newton’s first law.
Procedure: (You should read the instructions below as well as those in the student handout, this handout contains more details.)
Pre-class: Engage (?)
Ask the following questions to introduce Newton’s First Law to your class:
What happens when you are riding in a car with a seat belt on, and the car starts or stops suddenly? What would happen if you were not wearing your seat belt? What is providing the unbalanced force in this example? Can you think of some more examples when your body is in motion and it is acted on by an unbalanced force?
In-class activity: Inertia – A Body at Rest
The basic procedure is described on the student’s handout.
Note that the objects move less when friction is reduced. This permits us to see that Newton’s First Law is correct. Your students will notice the objects move hardly at all when the paper is pulled from under the glossy-covered book and a little more when they pull it from under the book with the non-glossy cover.
Extension Activity:
Go play air hockey. This is a perfect example of a frictionless surface. Ask the students the following: Why does the puck stop when the air stops? What makes it frictionless? Would the puck go on forever if it could? (If the walls of the table didn’t stop it.) How is this an example of Newton’s First Law?
Assessment:
Points / Newton’s First Law: Experimenting with Inertia!4 / Performed all suggested steps in the procedure, included observations and thoughtful answers to questions.
3 / Performed all suggested steps in the procedure, included observations and answered 2 or 3 questions.
2 / Performed all suggested steps in the procedure, included observations and answered 1 or 2 questions.
1 / Described some observations from the experiment, but observations where sloppy and or incomplete.
0 / Nothing turned in
Answers:
For all cases the book should move little, if at all.
Explain to your students the reasons for the results they have observed. The book did not move because of inertia, which is explained by Newton’s First Law of Motion: A body at rest will remain at rest unless acted upon by an outside force.
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Rev. 2/1/2006
Student Handout:
Newton’s First Law: Experimenting with Inertia!
This activity will help you learn all about Newton’s First Law of Motion. In this experiment you will discover the properties of inertia. In it, you will try to remove a bookcover from under an object without moving the object on top. Magicians do this all the time. Remember seeing a magician pull a tablecloth out from under a pile of dishes? Was it magic or science?
Before you begin, write down on your worksheet what you think will happen. Try to explain the scientific reasons for the outcome you predict.
Materials:
· one bookcover or large piece of smooth paper
· one book with a hard, glossy cover
· one book with a rough or non-glossy cover
· objects to place on the bookcover
Procedure:
1. Place the bookcover (or piece of paper) on a flat, smooth surface.
2. Put the book with the glossy cover on top of the bookcover.
3. Quickly (and in one smooth motion) yank the bookcover out from under the book.
4. Record what happens.
5. Do the experiment again, this time putting other objects on top of the bookcover.
Observe what happens and write your answers to the following questions on your worksheet
Does mass (weight) have any effect on the experiment?
Does the type of object you add have any effect? Why or Why not? Is so, in what way does it affect the object?
6. Try the experiment again using a book with a rough or non-glossy cover. What do you notice? Can you explain how these different results relate to Newton’s First Law of Motion? What is the unbalanced force in this experiment?
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Rev. 2/1/2006
CAN WE ADD ADDITIONAL EXPERIMENTS IN WHICH THE STUDENTS DO NOT PULL IT OUT QUICKLY AND OBSERVE WHAT HAPPENS? THEN THEY CAN COMMENT ON THE EXTERNAL FORCE (FRICTION) WHICH IS CAUSING THE LAW TO BE VIOLATED.
Add standards stuff here.
References:
Copies of these materials, along with additional information on Newton’s Laws of Motion and Law of Gravitation, are available on the Swift Mission Education and Public Outreach Web site: http://swift.sonoma.edu/epo/
• NASA Web sites:
NASA’s official Web site - http://www.nasa.gov
Swift Satellite - http://swift.gsfc.nasa.gov
• NASA Education Resources:
Swift’s Education and Public Outreach Program - http://swift.gsfc.nasa.gov/epo
Imagine the Universe! - http://imagine.gsfc.nasa.gov
The Space Place http://spaceplace.nasa.gov
NASA’s Central Operation of Resources for Educators (CORE):
http://education.nasa.gov/edprograms/core/home/index.html
NASA’s Space Science Education Resource Directory:
http://teachspacescience.org
• Newton’s Laws of Motion:
http://www-istp.gsfc.nasa.gov/stargaze/Snewton.htm
http://www.grc.nasa.gov/WWW/K-12/airplane/newton.html
• Newton’s Law of Gravitation:
http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html
• Newton in the Classroom:
http://www.physicsclassroom.com/Class/newtlaws/newtltoc.html
http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l1a.html
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