A MOVING EXPERIENCE - FORCES AND INERTIA
Grades 5 - 6

In this lesson, the students will have the opportunity to consider the first part of Newton's First Law of Motion, the Law of Inertia of objects at rest, which states that every object remains at rest unless acted on by a force. The video gives the students several examples to illustrate the law of gravity and its consistency. Activities to correspond with and extend the understanding of the concept of inertia include predicting and then testing the action of balls of various weights and sizes being released at a forty degree angle on an inclined plane, pulling paper out from under a glass of water and other weights at different speeds, hitting a block on the bottom of a stack of blocks, catching a coin on the elbow, and other experiments to show the effect of various forces on objects. After doing or watching these experiments, the students should be able to predict the effect various forces have on objects that are originally at rest.

3-2-1 Classroom Contact: Motion and Forces: Play Ball (Children's Television Workshop)

Students will be able to:

• identify and explain the first part of Newton's First Law of Motion (also known as the Law of Inertia of objects at rest) that states that every object remains at rest unless acted on by a force;
• use experimental materials to experience the law, first making predictions, testing them, and writing out the results of their activities and their observations of the experiments;
• extend their understanding to explain life situations like ski jumper's skills or the force it takes to push a stalled car or to get a rocket ship off the ground.

per class:

• chalk and blackboard or
• dry board and dry board markers
• eraser
• glass with water
• file card
• ten coins
• pack of 8/5 x 11 in. paper
• pencil
• bottle with a small mouth and neck
• brick
• rubber band
• six magazines
• heavy book
• sheets with directions for each activity group
• meter ramp
• balls of different sizes and weights
• target container to catch balls
• broomstick
• cotton string

per student:

• several sheets of paper
• one pencil

• inertia - an object's resistance to changing its velocity (in our case, the resistance of an object at rest to moving)
• force - a push or a pull
• Newton's First Law, part one - every object remains at rest unless acted upon by a force
• gravity - a force that objects have on each other

Have the students sit in groups of four and explain that during this class they will be expected to do some individual work and writing, and also some group work. Ask each group to choose a chairperson, a recorder, a reporter and a hands-on worker. The chairperson's job will be to keep the group on track and to lead the group work. Ask the hands-on worker to come up to get a pencil and several sheets of paper for each member of the group.

Explain to the students that from the time people can talk, they always ask why things happen. Scientists are people who devote their lives to asking "why" and experimenting to find out the answers. Whenever we do that, we are scientists, too. Say, "Isaac Newton was born in England in 1642, about the time our American colonies were being founded. He started asking "why" early in his life and he never stopped. One of the things he wondered about and experimented with was motion - how and why things moved. We are going to consider some of these questions today and do some experiments to help us get a clearer idea of them."

Direct the students' attention to a demonstration area where all can see. Place an index card on a glass of water. Put a coin on top of the card and very quickly pull the card off the glass in a straight line. (The coin stays in place, but without the card to hold it up, it falls into the water.) Ask the students to write down individually what they saw and why they think it happened that way.

After a few minutes, have the students within each group share what they have written with the chairperson in charge. Their task is to come up with a group explanation for what happened and why. The note taker takes this down.

When this is accomplished, have the reporters give the groups' responses. Write them on the board and accept all responses.

The focus for viewing is a specific responsibility or task(s) students are responsible for during or after watching the video to focus and engage students' viewing attention. To give students a specific responsibility while viewing, say, "When the video starts, you will see two students, Stephanie and Lee, doing some experiments with motion. Watch to see if you can see any connection between their experiments and what was going on with the coin and the glass.

BEGIN the video with Stephanie sitting looking at a ball on a table, just before she says, "Believe it or not, this is an experiment." After Lee says, "...a different kind of force, gravity," PAUSE. This will give the students time to think about the connection between the coin and glass experiment and the experiments Stephanie and Lee did.

Ask the students to discuss the question in their groups. After a couple minutes, let the groups' reporters share the gist of their groups' discussions. The students should notice that gravity caused the coin to drop into the glass when there was no card to support it. They will probably mention that the card was pulled away so fast, the coin didn't have time to move with it.

Tell the students that they will now be watching a section of the video showing examples of the gravitational force.They will need to watch for five examples of gravity. RESUME the video. Lee says, "Our planet is really grabby." PAUSE after Lee says, "...and it always pulls with the same force." This will give the students time to list the examples they have seen.

Say, "In each group, come up with five examples of gravity shown in the video. Then add two more that your group can think up on your own. Recorders, start writing." After a few minutes, have the reporters give their lists and write them on the board, one column for the video examples, one column for the new examples.

Tell the students that in the next segment, Stephanie and Lee prove a very important property of gravity. Say, "Let's watch to see if we can learn what this property is and how these young scientists prove it."

RESUME video with Stephanie saying, "So, gravity is something we can depend on." PAUSE after she says, "That helps us predict the movement of objects," to make sure the students understand that gravity is a force that is consistent.

Say, "Discuss in your groups what Stephanie and Lee proved about gravity." After a minute or so, ask the students to respond and discuss the consistency of gravity.

Say, "Here's a problem for us to work on. In the video we saw the same kind of ball shot through the hoops. What if we used different kinds of balls - different weights and sizes. Would that affect the consistency of gravity?"

Set up the ramp at a forty degree angle on a table or desk. It can be made of such things as two meter sticks taped together, or of a portion of a plastic rain gutter marked off to a meter's length, either leaning on a pile of books or a storage box. Have the lower end of the ramp at the edge of the table or desk. Have several balls - marbles, balls made of wood, cork, metal, a ping-pong ball, a nerf ball, a baseball - on hand.

Say, "Will balls of different sizes and different weights land in different places when released from the same spot on a ramp?" Ask for predictions. Have the groups talk it over and then take a tally making a quick graph on the board with columns saying Same Heavy Farther Heavy Closer or whatever the students mention. Discuss the students' reasons for their predictions.
Release one ball from one meter's height. Place the target container on that spot (or mark the spot with masking tape). Release all other balls from exactly the same height and in exactly the same way. (This is a good time for mentioning controlling variables in scientific experiments.)

The balls follow the same path and land in roughly the same place. The force of gravity pulls each ball down he ramp at the same speed. The ball continues to move forward as it falls. Occasionally a very light ball will encounter air resistance like the proverbial feather which needs a vacuum to drop at the same speed as a penny.

After the students have observed and discussed this experiment, have them return to their seats and write up what happened: the question asked, will balls of different sizes and weights land in different places when released from the same spot on a ramp?, their original prediction, what they observed, their conclusion based on the observation.

For the students who finish early, have this question posted on the board: Why don't ski jumpers hit the same spot when they race down a steep ramp into the air? Have them write the answers and then, when most students are finished writing up the experiment, discuss the question.

Say, "After Newton observed some of the things we have observed, he wrote them down, and some of his observations have been called 'laws' ever since. We have experienced a couple examples of his First Law also called the Law of Inertia.

"In Stephanie's first experiment, the ball stayed in the same spot on the table. This illustrates the Law of Inertia for objects at rest which states that every object remains at rest unless acted upon by a force. Why was her experiment so boring? What could have happened to cause the inertia of the ball to be broken?

"So, in the video, various forces were discussed. Lee showed how to apply several kinds of force to a ball, and Stephanie showed how a different kind of force called gravity also affects the inertia of an object. They both proved that the force of gravity is consistent, and we proved that gravity affects objects of various sizes and weights in the same way.

"Let's see how Stephanie and Lee conclude their experiments." FAST FORWARD and BEGIN the video as Stephanie and Lee sit looking at the ball on the table. Stephanie says, "Remember this experiment?" Stop the video when Lee says, "...it's consistent and predictable."

Say, "We have a few more activities to do today that will push our understanding of inertia and gravity a little farther."

Note to the teacher: Included are five activities for the students to do as groups and a culminating activity to use with the whole class which could be used as an assessment tool. Because of time constraints, these could be done on another day. The last part of the video could be kept until the end of the activities to bring closure to the whole process.

Each group will go to a work station and follow the instructions on the sheet found there. The chairperson or reporter will read the instructions, the hands-on person will be in charge of the experiment (the rest of the group may need to assist, depending on the experiment), and the recorder will write down the results on the sheet. The chairperson will be in charge of asking the group to predict what will happen before actually doing the experiment.

Activity One: Brick on a String

Give students a brick with a string (one meter in length) tied around it. The free end of the string will be tied to a rubber band. Place the brick on a carpeted floor and pull on the rubber band. Watch very closely. What happens? Why?

Note to the teacher:The rubber band stretches until the brick starts moving. As it is pulled further it stretches less because the initial inertia of the brick has been overcome making it easier to keep the brick moving. You might bring to the students' attention how hard it is to get a stalled car moving by pushing it. Once its inertia is broken, however, it's easier to push.

Activity Two: Move It Slowly

Give students several sheets of paper three inches wide and about eleven inches long. Place one sheet near the edge of the table, with about four inches extending over the edge. Put a bottle with a small mouth and neck upside down on the paper near the edge of the table. Take a pencil and place it in the loose end of the paper and carefully roll the paper around the pencil. Keep rolling very slowly until the rolled paper gets to the mouth of the bottle. Keep going. What happens? Why?

Note to the teacher: the paper will move out from under the bottle because inertia tends to keep the bottle upright, right where it was to begin with, so long as you move slowly and carefully.

Activity Three: Move It Out

Give students several sheets of paper and a heavy book. Place one of the sheets on the edge of the table, and put the book on top. Grasp the edge of the paper and pull it very quickly from the table. What happened to the book? Why?

Note to the teacher: The book remains stationary because moving the paper so quickly did not overcome the book's inertia.

Activity Four: Catch the Coin

Put several coins on the table. Place one coin on your elbow, holding your arm outstretched, parallel to the floor with your hand open, near your face. In one sudden, very quick move, drop your arm down and catch the coin. You will have to practice a few times to get the knack. What's going on here?

Note to the teacher: the coin, being still, tends to remain in the same position until gravity pulls it down. If you move very fast, you can beat gravity.

Activity Five: Grab the Mag

Take a stack of magazines. Have one of the magazines in the middle of the stack stick out a little. Pull that magazine out very quickly. What happens? Why?

Fix the stack again with one magazine sticking out. Pull it out slowly this time. What happens? Why?

Note to the teacher: when the magazine is pulled out quickly, the inertia of the magazines on top keeps them in the same position, but gravity pulls them down. When the magazine is pulled out slowly, the force of the pull has time to spread out to the magazines on top, overcoming their inertia as well, and they move.

After the groups have an opportunity to do at least three of these activities (in a classroom, they could be left out for students to experiment with during specified times), conclude with a discussion of the results. The groups will turn their sheets in with the names of the students in the group included.

There may be questions about moving objects and inertia, the second part of Newton's First Law of Motion, and that's another whole lesson.

As assessment, or just a culminating activity, have the students go back to individual seats and to their individual papers. Have several lengths of cotton thread, about sixty centimeters each, on hand. Tie one end of one thread to a broom handle and the other end to a block. Tie another thread to the block, letting the end dangle freely. Have volunteers help hold the broom handle about head height. Ask the students to predict which string will break first when you pull on the dangling end.

First do it very quickly. What happens? Why?

Then retie the threads and do it very slowly. What happens? Why?

Students could write about this as individual assessment pieces, or the class could discuss the experiment together.

• Invite a coach from a local high school to visit or send some of her/his students over to discuss how they overcome inertia to pole vault, make baseballs, footballs, etc. go where they want them to go, or run in a relay. There may be many other examples to demonstrate how gravity always needs to be taken into consideration when playing sports.
  
  
• Ask an auto mechanic to visit, or visit a garage, to have the person explain what it takes to start a car moving (mechanically this time - not with a push), and once it's running, how the mechanism changes.
  
  
• Ask a dance instructor to visit (especially if there are some of his/her students in the class) to demonstrate how dancers do those graceful lifts and other moves, taking inertia and gravity into account.
  
  
• Ask ice-skaters how they start.
  
  
• Ask gymnasts when they have to take gravity into consideration.
  
  
• Visit a high school or college physics lab to have an instructor demonstrate the penny and the feather falling in a vacuum, or other examples of gravity.

Physical Education:
Discuss what the class has been learning with their phys ed teacher, and ask for suggestions for activities that demonstrate Newton's First Law.To extend the ball throwing idea, show the rest of 3-2-1 Classroom Contact: Play Ball to the class. The section where the softball pitcher demonstrates putting spin on the ball, and the physics demonstrations connected with it are very useful.

Social Studies:
Conduct research on the world in the seventeenth and early eighteenth centuries when Isaac Newton lived. How did his discoveries affect people's lives?

Literature/Art:
Read aloud the short biography about Isaac Newton entitled, "The Short Giant," in Mathematicians are People Too by Reimer and Reimer (Dale Seymour Publications). Have the students illustrate parts of Newton's story to make a storybook of his life. Share the book with a younger grade.

Science:
Research the amount of force it takes to get a rocket ship off the ground.

Master Teacher: Mary Gene Devlin
Deerfield Elementary School, South Deerfield, MA