Investigation Sequence

Title

Simple Machines

Written by:

Alicia Powers and Jessica Probasco                 Date

 

Focus Questions

What is a machine? What do machines do?

Concepts

Content: Earth, Physical, & Life

Contentconcepts

Cross cutting concepts

unifiedproceessconcepts

Science Practice

inquiryconcepts

Personal, Social, Technology, Nature of Science, History

otherconcepts

Background information

Simple machines facilitate the transfer of energy. Machines cannot put out more work than is put in. Simple machines can increase force, but not work. No machine is 100% efficient. An inclined plane is used to reduce the amount of force needed to lift an object over a distance. A pulley changes the direction of the force, a fixed pulley is a wheel with a rope or belt wrapped around it, a movable pulley has a series of lifting strands, the more lifting strands it has, the less effort that is needed. A lever is used to change the direction of the force needed to lift an object. The location of the fulcrum determines how much effort is gained.additionalinfo

Activity Sequence

1. Inclined Plane One
2. Inclined Plane Two
3. Catapult Activity
4. Jumping Coin Trick
5. Pulley Activity
6. Tug of War Pulley
7. Messages on a Pulley

Activity Descriptions

Activity One
Inclined Plane One
Materials: 1 piece of paper, piece of cellophane tape, ruler, pencil, highlighter, and scissor for each student.
Procedure:
1. Ask the students what type of machine they could construct using the materials given.
2. Ask the students what type of simple machine they have just constructed and how they could use it.
3. Discuss the advantages and disadvantages of the machine.
4. Discuss where the machine is used and why it is used in that situation.


Activity Two
Inclined Plane Two
Materials: Textbooks, plywood or cardboard, wooden blocks.
Procedure
1. Ask the students how they would lift a stack of books from the floor to the top of their desks.
2. Discuss the possible machines that could be used to accomplish this task.
3. Give the students the materials and have them create a machine from those materials that can be used to move the books.
4. Give students time to work in small groups.
5. Come back together and have each group explain their machine. Discuss the advantages and disadvantages of each set up. Did the set ups have steep or gentle slopes? Have each student try the different machines and rank them in order from most difficult to move the books to least difficult.
6. Have students discuss what they have learned about how inclined planes should be built and when they are most effective.


Activity Three
Catapult Activity
Materials: Ruler, pencil, two large coins meter stick
Procedure
1. Create a lever by placing the ruler on the pencil. Discuss what type of machine has just been created.
2. Ask the students how they could set up an experiment to discover where on a lever they should apply pressure to get the most lift on the weight by using two large coins.
3. Discuss possible ways to record data.
4. Students should conclude that if they place one coin on one end of the lever and drop the other coin on the other side they should be able to record how high the other coin will bounce
5. Repeat the exercise, dropping the coin at various locations on the ruler.
6. Record student’s results on the board. Discuss any discrepancies.
7. Ask where they would drop the coin for optimal height.
8. Repeat the exercise using a meter stick and compare the results.
9. Take the students outside to the playground seesaw. Ask them what they have learned about levers can tell them about where they should sit on the seesaw to lift a classmate. Have students demonstrate and explain their reasoning.


Activity Four
Juice Can Activity
Materials: Juice can, board, books
Procedure
1. Refer the students back to Activity Three. Ask them to again create an experiment, using the given materials, to discover how the placement of the fulcrum affects the amount of force needed to lift an object. Probe them until they reach something close to the following procedure.
2. Have the students make a lever using the board and juice can.
3. Place four books on one end. Add books to the other end one at a time until the weight on the other end is lifted.
4. Record how many books were needed to lift the weight and the location of the fulcrum.
5. Have the students change the location of the fulcrum and add books one at a time until the weight is lifted. Repeat process three or four times.
6. Ask students if the weight is easier to move with a shorter, longer, or same length force arm.
7. Discuss what was learned.


Activity Five
Pulley Activity
Materials: string, pencil, sewing spool, strong stick
Procedure
1. Have the students construct their own pulley from the given materials. Allow time to experiment before bringing the students together to discuss their machines.
2. Have the students share their machines, what was similar and different about each.
3. Discuss how the pulley makes work easier.


Activity Six
Tug of War Pulley
Materials: 2 broomsticks, 5 meters of rope
Procedure
1. Give two students each a stick. Tie one end of the rope to one of the sticks. Have the students face each other, holding the sticks, with two hands, horizontally in front of them, about two feet apart.
2. Wrap the string around each stick, ask the students to pull backwards as you continue wrapping the rope around each stick.
3. Discuss what happened. Record results on the board. Discuss any other ways in which to record their data.
4. What happens when the number of wraps around the sticks is increased?
5. What are some practical uses for this machine?


Activity Seven
Messages on a Pulley
Materials: two thread spools, 40 feet of string, 2 round pencils, paperclips, message
Procedure
1. Put the pencils through the thread spool centers. Tie the ends of the strings together to make a loop. Have one person hold the ends of one pencil, another person holds the ends the other pencil
2. Wrap the string around the spools to create a pulley system.
3. Give the students paperclips and paper to write a message. Have them experiment with the pulley until they can get their message from one person holding a pencil to the other person holding a pencil.
4. Discuss the efficiency of such a system and what other uses it may have.

Dr. Robert Sweetland's notes