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Weigh-In and Worlds: A Rocket Club Argues About Gravity

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Weigh-In and Worlds: A Rocket Club Argues About Gravity

Use launch day weigh-ins and a world-builder simulator to argue about gravity.

Launch day and the weigh-in

Read the club notes and study Table 1. Then answer the questions.

Launch Day Notes: Why Does Every Rocket Come Back?

1Every April, the Mesquite Flats Rocketry Club launches model rockets from a dry lakebed outside town. Spectators stand behind a rope 10 m from the launch pads. Eighth grader Sunniva Kowal keeps the club's launch log. This year one rocket was launched straight up, and two were launched from rods tilted slightly away from the crowd. The straight-up rocket climbed, stopped for an instant high above the pad and fell back toward it until its parachute opened. The tilted rockets climbed on a slant, curved over and came back down to the lakebed farther away. Once their parachutes opened, the wind carried them sideways, but they kept drifting down until they landed.

2Before any rocket flies, it goes to the range safety table. Club advisor Mr. Desta Wolde hangs each rocket, motor included, from a spring scale marked in newtons (N). The scale shows how hard Earth pulls on the rocket, which is the rocket's weight. He hangs every rocket twice, and the two readings have always matched. Table 1 shows four of this year's rockets. The club follows a common safety rule: a motor's average push must be at least 5 times the rocket's weight, so the rocket leaves the launch rod fast enough to fly straight.

3Between launches, the members tried a world-builder simulator on the club laptop. It lets a user set the mass of an imaginary world while keeping the world exactly the same size as Earth. With the air turned off, Sunniva launched the same 0.50 kg rocket straight up again and again. Each time, it was moving upward at 28 m/s when its motor burned out. The simulator reported how hard the world pulled on the rocket and how much higher the rocket coasted after burnout before it stopped and fell back. Table 2 shows her runs. She checked each run twice and got the same numbers both times.

4Club member Jalen Pruitt watched the parachutes drift and had his own idea. "Gravity is really just air pressing down on things," he said. "Out where there's no air, a rocket would keep going up forever. And how much stuff a planet is made of has nothing to do with it."

Table 1: Range Safety Weigh-In
RocketMass (kg)Weight on scale (N)
Dart0.10.98
Comet0.21.96
Heron0.353.43
Thunderhawk0.6?
1.
Use paragraph 1. Circle the three observations that are evidence that gravity pulls the rockets toward Earth.

2.
Use the pattern in Table 1 to find the missing value.

The weight of the 0.60 kg Thunderhawk on the spring scale is about N.

3.
Which statement best describes the pattern in Table 1?
Question 3 options
4.
A motor has an average push of 12 N. Use the safety rule in paragraph 2 and the pattern in Table 1. Sort each rocket.

The world-builder simulator

Study Table 2 and use paragraphs 3 and 4 and Table 1 to answer the questions.

Table 2: The 0.50 kg Rocket on Worlds the Size of Earth (air off)
World mass (Earth = 1)Pull on rocket (N)Climb after burnout (m)
0.52.4580
14.940
29.820
4?10
5.
Use the pattern in Table 2 to find the missing value.

On the world with 4 times Earth's mass, the pull on the 0.50 kg rocket is N.

6.
Which conclusion fits Table 2 best?
Question 6 options
7.
Why did the simulator keep every world the same size as Earth?
Question 7 options
8.
Use Table 1 and Table 2. Suppose Sunniva runs the simulator with the 0.10 kg Dart on the world with 2 times Earth's mass.

The pull on the Dart would be about N.

9.
Sort each piece of evidence by the claim it supports best.
10.
Reread Jalen's idea in paragraph 4. Do you agree with him? Write an argument with a claim, evidence from both tables and the launch observations, and reasoning about what gravity is and what its strength depends on.