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Lesson 4 Grades 6–8

Drag and shape

Worksheets (PDF) Open Rocket Builder

On this page
  1. Standards
  2. I can…
  3. Words to know
  4. Materials
  5. Steps
  6. Check for understanding
  7. Teacher notes

Standards

Code In plain words
MS-ETS1-2 Evaluate competing designs with a systematic process.
MS-ETS1-3 Analyze test data to find the best features of several designs.
6.SP.B.4 (math) Display data (bar graph or dot plot).

Practice: analyzing and interpreting data. Crosscutting concept: structure and function.

I can…

Words to know

Materials

Straw-rocket supplies, a squeeze-bottle launcher (bottle + straw sealed into the cap with clay), a tape measure, a kitchen scale (optional), safety glasses, W4.

Steps

  1. 1Teach10 min
  2. 2Nose-cone test20 min
  3. 3Fin test15 min
  4. 4Rocket Builder5 min
  5. 5Wrap up5 min
55 minutes · learn plan hands-on wrap up

1Teach10 min

Read aloud

Four things make drag bigger: speed, a bigger front, a blunt shape, and roughness. Fins keep a rocket stable, but every fin adds drag and weight, so designers want fins that are just big enough. Today: change one thing at a time.

2Nose-cone test20 min

Nose-cone drag test: flat, cone and round noses on straw rockets of the same mass; air piles up in front of the flat nose; each is launched from the same squeeze-bottle launcher at the same angle, three trials each, and the mean distances are compared Same mass, three noses flatmost drag air piles up coneless drag roundless drag flies this way The fair test 30° squeeze same launcher, same angle 3 trials each: mean distance flat cone round
Nose shapes and drag: a blunt nose piles up the air; a pointed or rounded one lets it slide past.
45°flight pathdistance: launch spot to where it first landsABCbox
The angle test. A squeeze bottle with a straw sealed into the cap · B protractor on a box · C straw rocket.
  1. Three identical straw rockets: flat, cone and round noses, same mass (add tape to the lighter ones).
  2. Same launcher, same angle. 3 trials each. Mean and bar graph on W4.

3Fin test15 min

No fins, 3 small, 3 medium, 4 large. 3 trials each. Record distance and "straight or wobbly".

4Rocket Builder5 min

Keep everything the same and change only the nose shape; build each. The score barely changes: at model-rocket speeds the fins matter far more than the nose.

5Wrap up5 min

Which design had the best features? Could you combine them?

Check for understanding

  1. Name three things that make drag bigger.
  2. A rocket goes twice as fast. How much bigger is the drag?
  3. Why must the three rockets weigh the same?
  4. Why not put huge fins on every rocket?
Answer key
  1. Speed, frontal area, blunt shape, roughness (any three).
  2. About 4 times.
  3. So only the nose shape changes (a fair test).
  4. Extra drag and weight lower the flight, and it can be over-stable and turn into the wind.

Teacher notes

  • What to expect: flat noses go shortest; cone and round are often close, so small differences may be luck. More trials or a fairer launcher (a book dropped on the bottle from a set height) help.
  • Extension (Advanced mode): drag = ½ × 1.2 × speed² × Cd × area. A 30 mm rocket (area ≈ 0.00071 m²), Cd 0.65 at 50 m/s: ≈ 0.7 N, about its own weight. In Advanced → Flight, set the drag coefficient to 0.5 and then 0.8, build each time and compare the predicted altitude.
  • Further resources: Apogee Components' free lesson Rocket Optimization (apogeerockets.com/downloads/PDFs/58-2.pdf).
  • Change one thing: the launch simulator's change-one-thing experiments fly the same rocket with one setting changed (drag coefficient, nose, fins) and compare the flights.

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