Inclined Planes and Wedges Lesson Plan

1. Stretch. Pray. Read & discuss Genesis 1:26-28 & Genesis 3:17-19.

2. Demonstrate the physics term "work." Tell a child to lift a heavy box filled with many heavy books in it and place the box on the table. It should be too heavy for him/her to lift. Ask for ideas on what s/he can do. S/he could take one book out of the box at a time until s/he can lift the box by herself and then put all the books back in the box. Another option is few people could help him/her. Have him/her get the box of book on the table either way. Regardless of which way we solve the problem, would the amount of work done the same? (Yes. Regardless of how we did it, we lifted the heavy box with its contents to the table.) Did the box weigh the same when two, three or four people lifted it? (Yes, it weighed the same, but the people shared the work.) When you were lifting the box to the table what force were you working against? (Gravity.) When we do work we use energy. Who used energy in doing the work of lifting the box? (Yes, everyone who helped had to use energy to get the work done.) Work, then, is defined as moving a mass over a distance. What work was done here? (This box, this mass, we raised (moved) 38 inches.)
PERSON 1: YOU WILL NEED: a heavy books filled box

3. Demonstrate the physics terms "power." Have half the children go to the dining room table by walking straight to it and the other half of the children go to the dining room table by running through the den and kitchen. Did both groups do work? (Yes.) Did everyone arrive at the table at the same time? (Everyone was pretty close.) Who had to use more power? (The group that ran.) That means the running group worked harder and used more power. Scientists define power as the time rate of doing work, and energy is the ability to do work. You can actually measure the work done by multiplying the force (in this case how fast you moved) by the distance moved.

4. Demonstrate the physic's term "force."
a. (*Practice this ahead of time!) Penny Trick: Set an index card over the mouth of a glass/cup. Set a penny on the card directly over the mouth. Have the children predict the movement/action of the penny if the paper is flicked off the glass/cup. Flick the card with your finger. Where does the penny go? Why? (The penny is at rest and wants to remain at rest. The flicking force is applied to the card, so the card moves and the penny drops into the glass/cup.) Objects at rest will remain at rest unless acted upon by an unbalanced force. Objects in motion will remain in motion at the same speed and direction unless acted upon by an unbalanced force.
b. A force is a push or a pull. Have one child lightly push another child. Have a third child push a fourth child harder. You are all demonstrating force. Physicists, who are scientists who study how things move, measure force in newtons or pounds. Which child exerted more newtons or pounds? (Yes, child #3.)
c. Who moved the furthest? What measurements do we use to measure distance? (Meters or feet)
d. Physicists measure work in joules or foot-pounds. Select a volunteer to hold up a 1 pound item 1 foot (12 inches) above his/her waist. S/he is doing 1 foot-pound of work. Select a second volunteer to hold up a 1 pound item 2 feet above his/her waist. S/he is doing 2 foot-pounds of work. Select a third volunteer to hold up a 1 pound item 3 feet (12 inches) above his/her waist. How many foot-pounds of work is s/he doing? Yes, s/he is doing 3 foot-pounds of work.
f. Physicists came up with the law of machines, which states that little effort applied over a long distance can lift a great weight over a short distance. What does this mean? Give me an example?
g. All simple machines transfer force. Some change the direction of force, while others change the strength of the force. Still others change both the direction and the strength. Most simple machines make work easier by allowing you to use less force over a greater distance to move an object. Some machines make work easier by allowing you to move things farther and/or faster. In these machines, a larger force is required, but over a shorter distance.
PERSON 2: YOU WILL NEED: 3 items that each weigh about pound (look in your kitchen), an index card, a penny or small circular disk toy, & a glass

5. Introduce simple machines. How many of you have ever visited an aquarium with dolphins, or sharks? What is the largest animal the aquarium had? How do you suppose the aquarium moves the animals from the ocean to their location or from one tank to another? If you were a marine biologist asked to transport a killer whale (orca) that is 22 feet long and weighs over 7 tons from the sea to your aquarium, what would you do? Some of you suggested using machines to move the whale. What do you think of when you hear the word "machine?" Why do we use machines? Machines make our work easier. Can you think of some examples? Many machines are complex, with lots of moving parts. All complex machines are made from simple machines. Some simple machines only have one part that doesn't move. Can anyone name a simple machine? Hold up each example as the type of simple machine is mentioned. If no one mentions one type, hold the item up and ask if anyone knows what type it is. There are six simple machines: inclined plane, wedge, screw, lever, pulley, wheel, and axle. Today we're going to focus on inclined planes and wedges.
PERSON 3: YOU WILL NEED: 1 example of each type of simple machine. Possible examples include a screw (screw), screwdriver (wedge), hammer (lever), toy car with wheels (wheel and axle), and window blinds (pulley). (You can just point to my window blind.)

6. Read about inclined planes: "Roll, Slope, and Slide: A Book About Ramps" by Michael Dahl
Ask how inclined planes help us. What are some examples?

7. Divide children into 2 groups. One group goes to the bottom floor and the other group goes to the middle floor. Have children take turns trying to carry the luggage up the stairs. Then place the board/box on the stairs and try to pull the luggage up the stairs over the "inclined plane." How does it compare? When might we use this? If there was someone in a wheelchair who needed to get over 4 steps to get inside a building, what could you do?
PERSON 4: YOU WILL NEED: 2 sheets of wood or 2 large flattened boxes (both of which would fit on my staircase & would cover at least a few stairs), 2 pieces of luggage filled with something heavy (like books)

8. How might an inclined plane be used to make moving a heavy object easier and therefore take less force? Divide children into 4 groups. Have children stack 3-4 books. Lean one more book against the stack to make an inclined plane. Have children tie a cut rubber band to the neck of the sack. Holding one end of the rubber band, lift the bag straight up to the top of the books. Have the partner measure the length of the stretched rubber strip. Put the bag at the bottom of the inclined book. Switch roles. Hold the end of the rubber band strip and slowly pull the bag up the inclined plane. Their partner should measure the length of the stretched rubber strip when the bag is almost at the top. Which time did the rubber band stretch the least? The farther the rubber strip stretched, the more force was being used. Distance is represented by the length of the incline plane and force is represented by the length of the rubber band stretch. Force x Distance = Work. When might you need to carry a heavy load up an inclined plane?
PERSON 1: YOU WILL NEED: 4 rulers, 20 books, 10 strong rubber bands (you'll need extras as they might break) that have been cut, 4 small bags filled with about 1 cup of rice, dried beans, dirt, or other heavier object closed with a twist ties

9. Mention how people building the pyramids would have used inclined planes & use pictures from "Great Ages of Man: Ancient Egypt by Lionel Casson." (This also has pictures of a plow, which we'll show later.)

10. Divide children into pairs. How can an incline plane reduce the force to items being lowered? Place newspaper next to each group. Hand each child an egg. What is the best way to get the egg to the ground? What do you think will happen if you drop this egg on the newspaper from a standing position? Let one child in each pair hold the egg and drop the first egg onto the newspaper. Now use the ramp to lower the egg to the floor. What happened? The ramp (inclined plane) helped lower the egg with less force so it didn't break as much. If desired, have each group roll their egg down incline planes of different heights and lengths. Ask, "When might you need to use an incline plane like this?" (If you're not limited by time, the children can then eat the hard-boiled eggs.)
PERSON 2: YOU WILL NEED: 10 hardboiled eggs, newspaper, & 4 ramps (We used sturdy pieces of cardboard.)

11. How much does the changing the height of an incline plane affect the force? Physicists call that your mechanical advantage. It's the length of your incline plane (ramp) divided by your height. Have one group measure how long their ramp is. Have one group lay their ramp on a few books and measure how high their ramp is. Have another group lay their ramp against the seat of the sofa and measure how high their ramp is. Have the third group lay their ramp on the top of the sofa and measure how high their ramp is. As a group, work out the mechanical advantage of the three groups. Compare which is better. Emphasize that a higher mechanical advantage means that you'll have to do less work to get the same result.
PERSON 3: YOU WILL NEED: calculator (optional), marker board with marker, & 4 rulers

12. Have each group lay their ramp on the ground and place their car at the top. How fast is the car moving? (It shouldn't be moving at all.) Now have each group place 5-10 books under their ramp so that each of their cars will slowly glide down the ramp. Finally have each group place their ramp on the top of the sofa and let them race their cars down. Let them repeat this a few times for fun. How does the angle change the time it takes for the car to slide down the inclined plane? When might you need to use an incline plane to assist you in this way?
PERSON 4: YOU WILL NEED: 4 ramps, 40 books, & 10 Hot Wheels type cars

13. Read a book about wedges: "Wedges to the Rescue" by Sharon Thales. Ask how wedges help us. What are some examples?

14. How might a wedge be used to make work easier? How does a wedge decrease the amount of force needed to penetrate a substance? Evenly cover 4 baking sheets each with about 1 pound of rice. Pass out a block and a wedge to each pair of children. Instruct them to pick up the block and the wedge and placing them in the rice, making sure both are touching the baking sheet and are submerged in the rice. Have them each take a turn pushing the block and wedge to the other end of the baking sheet, paying close attention to the amount of effort used. Did you notice any differences? Was it easier to move the rectangular block or the triangular block through the rice? (Triangular) What happened to the rice as the triangular block was pushed through it? Where did it go? (It was pushed to the sides) How is a wedge like an inclined plane?
PERSON 1: YOU WILL NEED: at least 4 pounds of uncooked rice, 4 baking sheets, 4 wedges, and 4 blocks

15. Explain that a wedge is a simple machine that is used to spread an object apart or to raise an object. It spreads things apart by exerting a great deal of sideward pressure in both directions as it enters an object. Cutting tools generally contain a wedge. Ask if anyone can guess what is probably the most important use for a wedge? (The plow.) Show a picture of a plow from the Egyptian book.

16. (If you have extra time) Pass out a sheet of paper to each child and have them write their name on it. Divide children into pairs. Have one partner make a paper airplane with a pointed nose and the other partner make one with a flat nose. Which travels further? How is a paper airplane a type of wedge?
PERSON 2: YOU WILL NEED: 10 pencils and 10 pieces of paper

17. (If you have extra time) Divide children into pairs. Give each pair a doorstop and let them try to open a close a door with the doorstop under the door and without it. What happened? Why?
PERSON 3: YOU WILL NEED: 4 doorstops wedges

18. Give each child a slice of an apple. Have them take one bite using their incisors (front teeth). Have take a second bite using their back teeth (pre-molars or molars). Which was easier? Your sharp incisors are like wedges. They slice into and divide the apple slice. Your pre-molars are like those square blocks we used to separate the rice. As children finishing eating their apple slices, let them each have a turn cutting other apple slices with a kitchen knife/butter knife and a paring knife. Which is easier to use? The thinner the tip/sharper the blade of a wedge, the better it will be at exerting equal pressure in both directions and slicing through what you want to cut through. That's why it's best to sharpen knifes, plows, hoes, etc.
PERSON 4: YOU WILL NEED: at least 4 apples, a cutting board, & a butter/kitchen knife and a paring knife

19. Sing Simple Machines Song (Tune: "Yankee Doodle")
(Variation of this song.)

When it's moved by force we call it work,
but here's what I've been told:
Use any simple machine to help and ease that heavy load.

CHORUS: Wheel and axle, pulley, wedge
Screw, inclined plane, lever
When you learn to use simple machines
You'll show you are so clever.

The inclined plane is like a ramp,
a ladder, stairs, or hill.
Increase the distance =
reduce the work.
Mechanical Advantage thrill.

The wedge is used to separate,
lift, or hold in place.
You use a wedge to cut your cakes,
Long and narrow = less force it takes.

Our levers come three different ways,
depending on the fulcrum.
Lift, squeeze, cut, pull, haul, or toss
to get all of that work done.

The screw just turns to do its job
- like opening your juice.
Or use the screw to hold things tight,
so that they won't get loose.

The wheel and axle turns around
to help you get things going:
Uphill, downhill, straight ahead,
your force or distance growing.

The pulley uses cord or ropes or even chains or strings.
Pull longer distance
With less force
To lift enormous things.

CHORUS: Wheel and axle, pulley, wedge
Screw, inclined plane, lever
When you learn to use simple machines
You'll show you are so clever.

PERSON 1: YOU WILL NEED: Words to the song printed in large print

20. Review what we learned.

If you'd like to create a Simple Machines lapbook this week, here are some options:

1. Lapbook cut-out for each simple machine at the end of this lesson plan. You will have to click on a button to download the pdf.
2. Mini-book on simple machines.You can make the pages into a lapbook.
3. Lapbook links for simple machines This is a great site for physics lesson plans and links!
4. Simple machines worksheets You can also use these for a notebook.
5. A coloring page of each simple machine You can use these for a notebook.
6. Simple Machines Lapbook from Hands of a Child This one costs money.

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