Students who demonstrate understanding can: Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.
Clarification statement: Examples of evidence for arguments could include data generated from simulations or digital tools; and charts displaying mass, strength of interaction, distance from the Sun, and orbital periods of objects within the solar system.
Assessment boundary: Assessment does not include Newton's Law of Gravitation or Kepler's Laws.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
Gravity is the only one of the everyday forces that never pushes. Every object with mass pulls on every other object with mass, from an apple and Earth to the Sun and Neptune. Middle school students build an argument, backed by evidence, for two claims: gravitational forces are always attractive, and they are stronger when the objects involved have more mass.
Evidence comes from data and simulations rather than formulas. Objects dropped anywhere on Earth fall toward its center. The Sun, which holds more than 99 percent of the solar system's mass, keeps every planet in orbit. Jupiter, the most massive planet, holds dozens of moons, while tiny Mercury and Venus have none. Astronauts weigh less on the Moon, which has much less mass than Earth.
Distance also matters, and charts of distance from the Sun and orbital period help show it, but the formal law of gravitation and Kepler's laws are left for later grades. The focus is a clear claim, relevant evidence and reasoning that connects them.
Astronauts float in orbit because they and their station are falling around Earth together, not because gravity disappears. Earth's gravity at the station is still strong.
Every object with mass attracts every other. Your pull on a pencil is real, just far too small to notice compared with Earth's.
Without air resistance, a bowling ball and a marble dropped together land together. Gravity pulls harder on the heavier object, but it also has more mass to move.
Some students link gravity to the atmosphere. The Moon has almost no air but still has gravity that holds astronauts to its surface.
A student weighs 450 newtons on Earth. On the Moon the same student would weigh about 75 newtons. Write a claim, evidence and reasoning about what this shows.
Answer: The weaker weight on the Moon (about 75 N instead of 450 N) is evidence that gravitational attraction is weaker when one of the objects has less mass.
Give groups a data card set for planets and moons: mass, number of moons, surface gravity, distance from the Sun and orbital period. Ask them to sort and graph the data to find patterns, then write a claim-evidence-reasoning argument and critique another group's.
Assessment items usually present a data table and ask which evidence best supports the claim about mass, or ask students to identify a flaw in someone else's argument. Remind students that evidence must be specific numbers or observations, not opinions.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: D) They are always attractive
Gravity always pulls objects with mass toward each other. It never repels.
Answer: A) Jupiter has much more mass than Earth
Jupiter's much larger mass gives it a stronger gravitational pull at its cloud tops.
Answer: B) Astronauts weigh less on the Moon, which has less mass than Earth
Comparing weight on objects of different mass directly links the strength of gravity to mass.
Answer: sun (also accepted: the sun)
The Sun contains more than 99 percent of the solar system's mass, so its gravity holds all the planets in orbit.
Answer: D) they and the station are falling around Earth together
Gravity is still strong at that height. The astronauts and station fall together around Earth, so the astronauts seem weightless.
Answer: yes
Yes. Every object with mass attracts every other object with mass, although a pencil's pull is far too tiny to notice.
Support an argument that the gravitational force exerted by Earth on objects is directed down.
Use mathematical representations of Newton's Law of Gravitation and Coulomb's Law to describe and predict the gravitational and electrostatic forces between objects.
A full lesson with slides, activities and an exit ticket on gravity depends on mass, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-PS2-4 with an answer key, ready in about a minute.
Make a worksheet βTurn gravity depends on mass into a quiz students answer online that marks itself, with a class summary for you.
Build a test βNo. The assessment boundary excludes Newton's law of gravitation and Kepler's laws. Students argue from data and patterns instead of formulas.
Data on mass, surface gravity, weight on different worlds, or orbits from simulations. Specific numbers make the strongest evidence.