Lesson 2 Grades 3–5
Up and down: forces on a straw rocket
- Timeabout 45 minutes
- WorksheetE2 Straw rocket forces
- Rocket Builderon the projector
Worksheets (PDF) Open Rocket Builder
Standards
| Code | In plain words |
|---|---|
| 3-PS2-1 | Test how balanced and unbalanced pushes change the way something moves. |
| 5-PS2-1 | Use evidence to show that Earth's gravity pulls things down. |
Practice: engaging in argument from evidence. Crosscutting concept: cause and effect.
I can…
- I can build a paper straw rocket.
- I can name the forces on a rocket: thrust, gravity (weight) and drag.
- I can use what I saw to explain why every rocket comes back down.
Words to know
- Gravity the pull of the Earth. It always pulls things down, toward the middle of the Earth.
- Weight how hard gravity pulls on something.
- Drag air pushing back on something moving through it.
- Apogee the highest point of a flight.
Materials
For each student:
- A strip of paper about 8 cm × 20 cm, a pencil, a drinking straw
- Tape, scissors, a small piece of cardstock for fins
- Safety glasses
- Worksheet E2
For the class: a projector with Rocket Builder open (Beginner mode).
Steps
1Hook5 min
Toss a ball straight up. Ask: Why does it always come back down? Would it come down in Australia too?
2Learn10 min
Read aloudThree forces act on a rocket. Thrust pushes it up. Gravity pulls it down: that pull is its weight. Drag is the air pushing back, like when you put your hand out of a car window.
When thrust is bigger than weight and drag, the rocket speeds up. When the push stops, gravity and drag slow it down. At the very top, called apogee, it stops going up for a moment. Then gravity pulls it back down. Everywhere on Earth, "down" means toward the middle of the Earth.
3Do: build and fly straw rockets20 min
- Roll the paper strip tightly around a pencil. Tape the seam. Slide the pencil out.
- Fold the top over twice and tape it shut. This is the nose. It must be airtight.
- Cut 3 small fins (about 3 cm long) from cardstock. Tape them around the bottom.
- Glasses on. Slide the rocket onto a straw. Aim up and away from people. Blow one sharp puff.
- Watch: does it go up, slow down, stop and come back down every time?
- On E2, draw an arrow for each force: on the launch, going up, and coming down.
4Wrap up with Rocket Builder10 min
On the projector, press ▶ Watch it launch. Call out each part as the class watches: liftoff, push (boost), coast, top (apogee), parachute, landing. Ask: What pulled it back down?
Check for understanding
- Which way does gravity always pull?
- Your rocket flew up and then came down. What is your evidence that gravity pulled it?
- Which force pushes a rocket up?
Answer key
- Down, toward the middle of the Earth.
- It slowed down, stopped at the top and fell back to the ground, every time. Nothing was pushing it down except gravity.
- Thrust.
Teacher notes
- Safety: glasses on for everyone in the room. Launch only on your signal ("3, 2, 1, launch!"). Never aim at a person, pet or window. Straws are for one person only.
- Make it easier: pre-roll the tubes for grade 3, or use a paper template with a line to roll along.
- Grade 5 argument: ask students to write a claim ("Gravity pulls things down") and two pieces of evidence (their rocket, a dropped ball, people in other countries see things fall too).
- Common mix-up: some students think the rocket "runs out of push" and that is why it falls. Gravity is pulling the whole time; it just wins once the push stops.
- Keep the rockets for Lesson 3.
- Force arrows: in the launch simulator (Simple mode on the projector), turn on the force arrows. Students see thrust, gravity and drag change size through the flight, the same arrows as on E2.