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Invisible Forces Unit
Mystery 1 of 5
How could you win a tug-of-war against a bunch of adults?
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How could you win a tug-of-war against a bunch of adults?
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DISCUSS: Tug of War

Can you think of any way for your team to win? Is there something you could do to make it harder for the adults’ team to pull?

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DISCUSS:

Is there some way to stop the adults from being able to push against the ground?

With any ideas you come up with, explain why you think that idea might work.

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Practice: Think about each action below. For each one, ask yourself: Is it a push or a pull? (Answers on next slide.)

squeeze
pinch
tug
smack
drag
lift


Can you come up with any other verbs where there's either a pull or a push?

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squeeze = push
pinch = push
tug = pull
smack = push
drag = pull
lift = It depends how you lift. You could push up on a thing to lift it, or you could pull on it too.
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Discuss: Do you have any ideas for how you could get the watermelon to burst using rubber bands?

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SPECIAL NOTE TO TEACHERS

The next slide features an Activity Video where students learn how to make "Hopper Poppers."

Constructing the hopper takes students about 20-25 minutes. Practicing using their hopper and then completing the "High Hop Score Card" takes an additional 20 minutes.

If your time is limited, there is a natural stopping point after Step 6. Have students write their names on materials, then collect them and resume the activity next science class.

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Beginning Complete!

You've completed the Exploration & Activity!

If you have more time, view the assessment, reading, and extension activity in the optional extras.

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Optional Extras

Below are ideas for extending this topic beyond the Activity & Exploration which you just completed.
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Extra Activity: Tug-of-War

Tug-of-war is a great way to give students a feel for forces. You’ll need a sturdy rope, a room with a slick floor, and masking tape. Use masking tape to mark the center of the rope and make a line on the floor.

Discuss with the students how to make two, evenly matched tug-of-war teams. Have the teams play tug-of-war, starting with the center of the rope directly above the line.

Then have a rematch with one simple change: The winning team must take their shoes off and play in their stocking feet. (They’ll feel like teachers on roller skates.)

If students mention friction here, let them know you’ll be exploring that topic fully in a future Mystery.

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Image & Video Credits

Mystery Science respects the intellectual property rights of the owners of visual assets. We make every effort to use images and videos under appropriate licenses from the owner or by reaching out to the owner to get explicit permission. If you are the owner of a visual and believe we are using it without permission, please contact us—we will reply promptly and make things right.

Exploration
watermelon by Mike Mozart , used under CC BY
kids playing tug-of-war by Image used under license from Shutterstock.com: Luis Louro
tug of war European championship by Tug of War Association
Olympic weightlifter by Simon Q
Soldiers playing tug of war by SFC Victor Aguirre
Marine playing a tug of war by Cpl. Matthew Callahan
teacher by Image used under license from Shutterstock.com: wavebreakmedia
Student teacher Tug-O-War by pittcaleb
roller skating elephant by Carol Buckley
push by Mark Doliner , used under CC BY
dough stretching by Joe Hall , used under CC BY
roller skates by Image used under license from Shutterstock.com: Julenochek
dog tug o' war by kellinahandbasket , used under CC BY
pile of watermelons by Mike Mozart , used under CC BY
half watermelon by The Chic Life
slow motion watermelon video by The Slow Mo Guys , used under CC BY
Overview
Grade 3rd
Topic Forces, Motion, & Magnets
Focus Forces
Print
Activity Prep

In this Mystery, students will see that by learning to think about pushes and pulls — forces — they can accomplish extraordinary things! In the activity, Hopper Popper, students make a folded piece of cardboard jump high in the air, propelled by the pulling force of a rubber band. They discuss the forces involved in making this “Hopper Popper” jump.

Preview activity

Number of students:
Pen
30 pens
Rulers
30 rulers
Scissors
30 pairs
Chipboard
Recycled cereal boxes also work.
Details
4 square feet
Rubber Bands (#16)
60 bands
High Hop Scorecard printout Print 30 copies
Hopper Popper Teacher Tips printout Print 1 copy
Launch Pad printout Print 30 copies

OPTIONAL SUPPLIES

Chipboard
Allows students to test a different Hopper Popper size.
Details
120 square inches
Rubber Bands (#32)
Allows students to explore how changing the rubber band size affects their Hopper Popper.
Details
30 bands
Prep Instructions

In this activity, each student will make their own Hopper Popper, but we suggest they work in pairs when they launch their poppers. Homeschool students can work on their own, but may need a partner to help when it comes time to launch their Hopper Popper. Some teachers choose to have students wear safety glasses for this activity since Hopper poppers can hop high!

Prepare the Chipboard

If you want your students to practice measuring, you can have them cut 3” x 6” rectangles from chipboard before you begin this Mystery. If you don’t have time for students to measure and cut rectangles, we recommend you cut the chipboard into 3” x 6” rectangles before class. It doesn’t take long if you use a paper cutter.

Supplies for Open-Ended Exploration (Optional)

At the end of the activity, we suggest that students change one variable to see how this affects their Hopper Popper. For this open-ended exploration, you can supply students with extra chipboard, extra rubber bands of different sizes, or extra rubber bands of different thicknesses. The Teacher Tips printout will help you guide students during this open-ended exploration.

Overview
Grade 3rd
Topic Forces, Motion, & Magnets
Focus Forces