LET'S PLAY POST OFFICE
Grades 3 - 8

Birthdays and holidays are always an exciting time for children, especially when the mailperson arrives with a special letter or package. Exactly how does the mail get from one place to another? This lesson investigates how simple machines assist in the sorting of mail. Students identify different simple machines being used and discuss how they can be combined to create complex machines.

Here's How,#11: The Postal Station

Students will be able to:

• define the following terms: lever, wedge, screw, inclined plane, pulley, and wheel and axle
• understand how simple machines can be used together to form more complex machines
• explain the functions of the six simple machines
• apply concepts learned to construct a device composed of simple machines which can move an object 10 feet

For each student:

• copy of Simple Machine Detective Form
• copy of A Tale from the Land of Douglassville sheet
• copy of Douglassville response recording sheet
• copy of Simple Machine Assignment sheet

For each group of students:

• 10 red tiles
• 10 blue tiles
• 10 yellow tiles
• 10 green tiles
• (or 10 identical items in 4 different colors to represent different denominations of stamps)
• a large variety of building materials such as rubberbands, paperclips, shoe boxes, cereal boxes, paper tubes

Brainstorm ways we are able to get objects from one place in the world to another. If the idea of using the mail service is not generated by students, prompt them by asking how they receive cards and letters from grandparents and friends. Once they have suggested the postal service, complete the postage stamp activity which accompanies this lesson. Students should receive a copy of the Tale from the Land of Douglassville sheet. After reviewing the directions with your class, provide students with the Douglassville response sheet to use while completing the project. Most students find the manipulatives helpful for organizing their charts. I usually have students work in groups of two or three, but each member of the group must complete a response sheet.

Vocabulary: with the help of knowledgeable students, or through teacher instruction, come up with a working definition and example for each of the six simple machines:
lever - a simple machine usually made of a board that is used to move objects
inclined plane - a simple machine with a flat surface that is higher on one end
wedge - a simple machine used to push objects apart
screw - a simple machine used to hold objects together
pulley - a simple machine with a wheel and a rope used to move objects up, down, or sideways
wheel and axle - a simple machine made of a rod attached to the center of a wheel used to move or turn objects

Explain to students they will be viewing a video which explains how letters and packages are sorted for delivery. To give students a specific responsibility for viewing, ask them to find as many simple machines being used as possible, using the attached Simple Machine Detective Form. Inform the students they will first view the video without sound in order to try to identify as many times as possible that a simple machine is pictured.

Make sure the volume of the television has been turned off to ensure students are focusing on the visual images being presented and not on the narration provided. Distribute the Simple Machine Detective Form and review the directions with students.

BEGIN the video when the red mailbox appears.

STOP the video after the packages have been dumped from the keying wagons and the girl appears. Have students share their observations with their classmates. If disagreements erupt over whether or not an observation is a variation of a simple machine, refer students back to the working definitions developed in the previewing activity.

REWIND the tape. Explain to students they are now going to view the video in its entirety, but this time with sound. Ask them to think about how their observations match what actually occurs as detailed through the narration of the video.

START the video after the mouse says, "She makes it sound so easy."

PAUSE after the narrator says, "... but a handwritten message is still special." Ask students to identify faster ways.

RESUME the video and PAUSE after the mouse says, "Didn't they have a post office back then?" Ask for ideas.

RESUME the video and PAUSE after the mouse says, "How do they deliver it so fast these days?" Ask for ideas.

RESUME the video and PAUSE after the narrator says, "The answer is here at the Gateway Postal Station." Have students look closely at the scene on the monitor and ask them to identify the simple machine that is being used. (Wheel and axle on the delivery truck. It is helpful to have students actually come up to the television screen and point to the simple machine they can identify. You may also place a piece of actetate over the screen and have them circle the object. This technique applies to all of the times students are asked to identify a simple machine throughout the video.)

RESUME the video and PAUSE as the forklift backs out of the delivery truck. Have students look closely at the scene on the monitor and ask them to identify the simple machine being used. (Lever on the forklift. A discussion might need to take place to remind students a lever does not always have to be made of wood.)

RESUME video and PAUSE as the bag of mail falls through the opening onto the conveyor belt. Have students look closely at the scene on the monitor and ask them to identify the simple machine being used. (Inclined plane.)

RESUME the video and PAUSE as the large wheel comes into view with the mail being spun around it. Have students look closely at the scene on the monitor and ask them to identify the simple machine being used. (Variation of a pulley.)

RESUME the video and PAUSE when the narrator says, "... eight pieces of mail goes by every second." Ask how many pieces of mail would go by in 10 seconds. (80) How many would go by in one minute? (480)

RESUME the video and PAUSE when the small wheel of metal with printing on it is held up. Ask students to predict what they believe the wheel is used for.

RESUME the video and PAUSE when the balloon says, "That's a good question, isn't it?" Ask students how they think the machine knows if there is a stamp on the letter or not.

RESUME the video and PAUSE after the black place marker is inserted into the mail being sorted. Have students look closely at the scene on the monitor and ask them to identify the simple machine being used. (Wedge.)

RESUME the video and PAUSE when the girl says, "What happens to letters with bad handwriting?" Ask for ideas.

RESUME the video and PAUSE when the narrator says, "... brings them up to a keying station." Have students look closely at the scene on the monitor and ask them to identify the simple machine being used. (Inclined plane.)

RESUME the video and PAUSE when the mouse says, "What's it going to do with them?" Ask for ideas.

STOP the video after the narrator asks what delivering mail might have been like during your grandfather's time and like today. Ask for ideas and comments from students.

Activity 1
Explain to students that they will be involved in an activity which requires them to use the information they have gained through the video and class discussions to construct a machine which will move a ball at least 10 feet. Tell students they may bring any materials they wish from home to construct their machine, but the machine must be made during assigned class time. Tell them to keep in mind some of the ways they saw simple machines being used in the video when they begin to design their machine. As a way to begin having students think about the project, suggest that other students have found it useful to collect and bring in cardboard tubes, cereal boxes, blocks of wood, cans, jars, rulers, pencils, books, rolling pins, and shoe boxes. Students may want to begin to lay out their design on paper prior to beginning the actual construction. Distribute the attached information sheet for students to take home.

On a subsequent day(s), allow time for students to construct their machines. It is important students be allowed to conference and discuss their team's ideas with peers when needed. Move from team to team to provide encouragement and to assess each member's knowledge of simple machines. Questions such as, What simple machines have you used to construct your complex machine? and How do you think they will work together to achieve the task? will provide good insight into individual thinking.

After all groups have completed the assignment, have each team attempt to accomplish the task. Discuss the results. Highlight the similarities and differences in results. Pose the following questions: What simple machine seemed to be used the most often? The least? Why? What might you do differently if you could reconstruct your machine?

Activity 2
After explaining the longer assignment, tell students that you are now going to put them into groups of four to design simple machines to move a ball 20 feet, using themselves as simple machines. Explain that each person in the group must become a simple machine and attach him/herself to another member of the team. I have found that it is helpful to give students a definition of attaching themselves to another member of the team. I have found it works well if you define it as one hand or foot touching at least one other member of the group. Once individuals have decided upon their role, they should work with team members to put "together" their machines, and then demonstrate for class members how the machine works. Tell students that the ball will be placed on the floor as its starting point. Discuss how this information is important, because should they decide to use an inclined plane, they will need to determine how the ball will get to the top of the plane.

Contact your local Post Office and ask them to help you set up a Wee Deliver Post Office at your school.

Ask parents of class members to come to school and explain how simple machines are used in their place of employment or at home.

Plan a field trip to a local business (newspaper office, bottling plant, canning factory) and have students see the use of simple machines in action.

Art: Design a school stamp that could be used in conjunction with the Wee Deliver program at your school.

Mathematics: Have students create their own countries and develop stamp denomination activities similar to the previewing activity.

Writing: Write a story about how the world would be different if there were no simple machines available.

Writing: Research Archimedes' quote, "If I had a lever big enough I could move the world," and write a report explaining what he meant.



RESOURCES
Adkins, Jan. Moving Heavy Things. Boston: Houghton Mifflin Co., 1983.

Barton, Byron. Wheels. New York: Crowell, 1979.

Hellman, Hal. The Lever and the Pulley. Philadelphia: Lippincott, 1971.

Miller, Lisa. Levers. New York: Coward McGann, 1968.

Owen, Wilfred. Wheels. New York: Time, 1967.

Scheele, Carl. Neither Snow nor Rain. Washington: Smithsonian Institute Press, 1970.

US Postal Service. Wee Deliver: The Story of the US Postal Service. Washington: US Postal
Press, 1986.

Weiss, Harvey. Machines and How They Work. New York: Crowell, 1983.

Master Teacher: Douglas Hoff
Mast Way Elementary School, Lee, NH

Click here to view the worksheet associated with this lesson.