Lesson Motion Commotion

Learning Objectives

After this lesson, students should be able to:

• Identify Newton's three laws and explain what each law physically describes with respect to motion.
• Predict results from the various motions presented in the activities and be able to explain why these motions occurred.
• Give examples of why Newton's laws are important to engineering.
• Relate the variables in the F = ma equation 

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

International Technology and Engineering Educators Association - Technology

State Standards

Introduction/Motivation

When Isaac Newton was 23 years old, he identified three traits of moving objects. His identification of these traits, now accepted as Newton's laws of motion, revolutionized science and transformed human understanding of the natural world. Newton's laws are universal, describing the motion of everything, everywhere!

Scientific application of Newton's laws led to advancements in every aspect of engineering, from building machines and structures to the functioning of airplanes and rockets. Sir Isaac Newton is the founder of the modern study of movement and balance because of his development of the three laws of motion.

Newton's laws hold true everywhere and at all times. Understanding the laws of motion helps us to understand what causes every movement we make throughout the day. The laws apply to ALL movement, from you, to a running stream, to a falling leaf, to a bird's flight. Having three laws that describe the why and how of all motion is an incredibly useful tool!

Lesson Background and Concepts for Teachers

Simply stated, Newton's three laws of motion are:

Law #1: Objects at rest will stay at rest, and objects in motion will stay in motion in a straight line unless they are acted upon by an unbalanced force. (law of inertia)

Law #2: Force is equal to mass multiplied by acceleration. (F = ma)

Law #3: For every action, there is always an opposite and equal reaction.

Newton's first law is also known as the law of inertia. It says that if you were to kick a ball and there were no forces acting on the ball, it would keep going in a straight line forever! This law is somewhat abstract because on Earth, invisible forces are always at work. Gravity, friction and air pressure are examples of "invisible" forces that act on objects everywhere. Therefore, objects on Earth are constantly changing direction, speeding up and slowing down — a ball does not keep going forever because there are forces acting to slow it down. Scientists and engineers must always keep in mind these "invisible" forces acting on the object's motion.

Newton's second law means that if you kick two balls that weigh the same, the ball you kick harder will go farther (that is, for a constant mass, exerting a greater force yields a greater acceleration). The second law also says that if you have a heavy ball and a light ball, you have to kick the heavy ball harder to make it go as fast as the lighter ball (that is, for a constant acceleration, a greater mass requires a greater force). The mathematical way to state this law is:

F = m x a

(Force = mass times acceleration)

If you hit a golf ball and a baseball with the same amount of force, which one would go farther? The golf ball! Why? Because the golf ball has less mass than the baseball, therefore less force is needed for the golf ball to achieve the same distance as the baseball.

Newton's third law is possibly the most widely known — for every action, there is an equal but opposite reaction. There is always a partner of forces at play: an action force and a reaction force. Even though this is possibly the most famous of his three laws, it is not necessarily the most intuitive. For example, when you walk on the ground (action force), the ground pushes up on you with an equal reaction force. You cannot see the force, and we are so accustomed to walking on the ground, we do not even realize there must be a reaction force that keeps us from sinking into the ground. Imagine sinking into the ground with every step we take! That's exactly what would happen if this third law were not true.

Associated Activities

• Catapults! - Students construct a catapult to demonstrate Newton's second law of motion and learn the relationship between force, mass and acceleration.

  Watch this activity on YouTube

• Action-Reaction! Rocket - This activity illustrates Newton's first, second and third laws of motion. Students construct a balloon "rocket" to see how the action force of air emptying a balloon causes a reaction force, which moves the rocket along a wire.

  Watch this activity on YouTube

• Couch Potato or Inertia Victim? - Students design a simple behavioral survey and learn basic protocol for primary research, survey design and report writing.

Lesson Closure

Ask the students to explain Newton's three laws of motion. Have them give some examples of what life on Earth would be like if these laws were not true. Ask the students why Newton's laws are so important to engineers. Have them write on the board at least three reasons why Newton's laws are important to engineers, or what has become possible with the understanding of these laws. (Possible answers: Has made it possible to build airplanes that fly, elevators that move, amusement park rides and roller coasters, cars that drive safely, seatbelts in cars, bridges and buildings that do not collapse; basically, Newton's laws are the foundation for all structures that move or are stationary.)

Vocabulary/Definitions

Acceleration: Rate of change in velocity with respect to magnitude, direction or both.

Force: Something that acts from the outside to push or pull an object. For example, an adult pulling a child in a wagon exerts a force upon the wagon.

Mass: The amount of material (matter) present in an object.

Assessment

Pre-Lesson Assessment

Discussion Question: Ask a question to get students to think about the upcoming lesson. After soliciting answers, explain that these questions will be answered during the lesson.

• When you kick a soccer ball up in the air, why does it come back down? Should it not just keep going? (See Background section to add more depth to this discussion.)

Post-Introduction Assessment

Question/Answer: Ask the students and discuss as a class

• Who came up with the three laws of motion? (Answer: Sir Isaac Newton)
• How old was Sir Isaac Newton when he came up with the three laws of motion? (Answer: 23)

Lesson Summary Assessment

Flashcards: Using index cards, have the student groups write Newton's three laws or questions that apply to one of the three laws. Have them write the appropriate law number or answer on the back of the card. Have the teams exchange flashcards. Each member of the team reads a flashcard, and everyone attempts to answer it. If they are right, they can pass on the card to the next team. Give the team five minutes to figure out, through teamwork, the answers to the flashcards. If they feel they have another correct answer, they should write their answer on the back of the flashcard as an alternative. Keep rotating the cards until all teams have had a chance to look at all the flashcards. Clarify any questions.

Lesson Extension Activities

Inertia Zoom Ball

In this hands-on demonstration of Newton's first law of motion, students use plastic bottles and string to see how force causes an object to change in motion.

Inertia Zoom Ball

More Power to You

Newton's third law of motion is illustrated in this hands-on activity in which students fuel a plastic bottle boat to move on water.

More Power to You

Library research project

Have the students research Sir Isaac Newton, write a book report and present their findings to the class.

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.