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Rover Weights on Three Worlds: Gravity and Mass

Grade 8 gravity practice: compare rover part weights on Earth, Mars and the Moon and argue that gravity attracts and depends on both masses.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS2-4

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
10 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use weight data to show that the pull of gravity grows with the mass of an object.
Students compare worlds to argue that the pull of gravity also depends on the mass of the planet or moon.
Students use observations to argue that gravity is an attraction between both objects.

How to use

Review the difference between mass and weight first, then let pairs read the two tables and agree on one pattern in each before they answer.

Curriculum

NGSS standard covered

MS-PS2-4

Argue from evidence that gravity is attractive and depends on the masses of the objects.

Preview

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Name Date

Rover Weights on Three Worlds: Gravity and Mass

Use weight data from Earth, Mars and the Moon to argue how gravity works.

The weight data

Read the design notes and study both tables, then answer the questions.

Design Notes: A Rover for the Moon or Mars

1The Northgate Middle School engineering club entered a design challenge to plan a small rover that could explore either the Moon or Mars. Club members Teodor Ramírez-Lund and Abebe Sorensen were in charge of the springs that hold up the rover's body. Springs must be strong enough to carry the weight of each part, so the pair needed to know how hard gravity would pull on the parts on each world. If a spring is too weak, the body sags onto the wheels; if it is too stiff, the rover bounces hard over rocks. Abebe planned to test each spring in the lab by hanging parts from it before the club chose a final design. Their advisor, Mr. Halvard Nkemelu, explained that mass is the amount of matter in a part and stays the same anywhere, while weight is the force of gravity on the part and is measured in newtons (N).

2The pair used a planet data app to find the weight of each rover part on the surface of Earth, Mars and the Moon. Table 1 shows the app's results, rounded to one decimal place. Table 2 shows facts about the three worlds from the same app, including the pull of gravity on a 1 kg object at each surface. Earth's mass is set to 1, so a world with a mass of 0.11 has 0.11 times Earth's mass.

3Mr. Nkemelu also shared three facts from real space missions. On the Moon, astronauts who let go of a tool or a rock saw it fall slowly back down to the gray dust. Earth and the Moon both circle around a shared point about 4,700 km from Earth's center, so Earth wobbles slightly as the Moon goes around it. On a space station about 400 km above Earth, astronauts float inside the cabin, even though a 10 kg backpack up there is still pulled toward Earth with about 87 N, compared with 98 N on the ground. The station and everyone in it are falling around Earth together.