How do mass and separation affect a gravitational interaction?
Submit: An evidence record, explanation and revision.
Related lesson: Motion and Forces
This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.
Teacher review guideBuild the idea
Gravity is an attractive interaction between masses. Both objects participate, even if one moves too little for us to notice. Qualitative comparisons require holding separation fixed when comparing masses and holding masses fixed when comparing separation.
Science / engineering practice
Argument from evidenceCore idea
Gravity is attractive and depends on interacting massesCrosscutting concept
Systems and system modelsEvidence and model inputs
Conceptual model cards, not measured force values: A, two small masses close together; B, one larger mass at the same separation; C, the original two small masses farther apart. The model predicts B stronger than A and C weaker than A. Observational source: NASA describes gravity as attraction that holds the solar system together.
Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.
Materials and preparation
Paper, graph paper or spreadsheet, and the linked readings.
Grade-level scope
No Newton or Kepler formula calculations at this middle-school performance expectation.
Do the work
- Read the NASA account and distinguish its scientific explanation from the supplied model predictions.
- Draw paired arrows pointing toward the interacting objects in A, B and C.
- Write a claim about mass using A versus B and a claim about separation using A versus C.
- Use orbiting and falling objects as two contexts for the same attractive interaction.
- Respond to “only Earth pulls” and state what evidence or measurements would strengthen the argument.
Learner worksheet
Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.
Check your reasoning
- Does the small object also pull the large one?
- Which comparison tests distance?
- Why can equal-size arrows represent different motion?
- Are these cards empirical force measurements?
Teacher review guide
Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.
- Claims that gravity attracts interacting masses.
- Uses controlled qualitative mass and distance comparisons.
- Connects source evidence and model with clear provenance.
- Addresses mutual interaction and a limitation.
Answer guidance for the reasoning checks
Does the small object also pull the large one?
Yes. The interaction is mutual.
Which comparison tests distance?
A versus C.
Why can equal-size arrows represent different motion?
Interaction forces are paired, but objects of different mass respond differently.
Are these cards empirical force measurements?
No. They are model predictions supported conceptually by the source, not original measurements.
Access, support and extension
Offer read-aloud support, labeled diagrams, larger print or an oral/recorded explanation while preserving the scientific reasoning. A partner or teacher can handle physical manipulation while the learner plans, records and interprets. Use a teacher-provided measured dataset only when its provenance and limitations are explicit; it does not replace conducting an investigation when that is the assessed practice. For greater independence, remove prompts and ask learners to compare a second explanation or test another justified revision.
Sources and standard reference
- Official NGSS MS-PS2-4 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.
- NASA: gravity
Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.