Gravity, Mass, Weight

Grade: 7

Duration: 70 minutes

Class size: 24 students

Subject: Science

---

Learning Objectives (aligned with Common Core and NGSS)

I can…

• Explain the concepts of gravity, mass, and weight and how they are related.
• Differentiate between mass and weight and describe how gravity affects weight.
• Calculate weight using mass and gravitational acceleration.
• Analyze real-life examples where mass and weight differ (e.g., Earth vs. Moon).

Standards Addressed:

• Next Generation Science Standards (NGSS):
  MS-PS2-2: Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.
  MS-PS2-4: Construct and present arguments supported by evidence to support the claim that gravitational force is attractive and depends on the masses of interacting objects.
• Common Core State Standards (CCSS) for Mathematics:
  CCSS.Math.Content.7.EE.B.4: Use variables to represent quantities in a real-world or mathematical problem, and write an equation to solve the problem.

---

Materials Needed

• Spring scales (24, one per student or pair)
• Set of standard masses (blocks or weights)
• Calculators
• Worksheet: Gravity, Mass, and Weight problems
• Whiteboard and markers
• Chart paper
• Video clip illustrating gravity (2–3 minutes)
• Access to a simulation applet or website (offline version recommended) on gravity and weight differences on Earth vs. Moon

---

Lesson Breakdown

1. Introduction & Engagement (10 minutes)

• Begin with a quick demonstration: Drop two objects of different masses simultaneously and ask students what they observe about their fall (expecting them to say they hit the ground at the same time).
• Show a short 2-3 minute video clip demonstrating gravity's role on Earth and the Moon.
• Pose a guiding question: "How are gravity, mass, and weight connected, and why do astronauts weigh less on the Moon?" Engage students in a brief class discussion.

2. Direct Instruction (15 minutes)

• Define and explain mass (amount of matter in an object, in kilograms) and weight (force due to gravity acting on an object’s mass, in newtons).
• Introduce gravity as a force that attracts objects with mass toward each other, with Earth’s gravity pulling objects down.
• Write the equation for weight: Weight (N) = Mass (kg) × Gravitational acceleration (9.8 m/s² on Earth)
• Use visuals and analogies (e.g., mass as amount of "stuff" in a bag, weight as how hard the bag pushes down on a scale).
• Connect this to the student's everyday experience (e.g., feeling heavier with a backpack).

3. Guided Practice (15 minutes)

• Students work in pairs with spring scales and masses to measure and record weight.
• Practice calculating weight using mass and gravity formula.
• Worksheet includes problems such as:
  • Calculate the weight of a 5 kg object on Earth.
  • Calculate the weight of the same object on the Moon (use 1.6 m/s² for Moon's gravity).
• Teacher circulates to provide support and clarify misconceptions.

4. Application & Higher-Order Thinking (15 minutes)

• Extensions: Challenge advanced learners with questions on why astronauts “feel weightless” in space although their mass remains constant.
• Use a class discussion to formulate explanations supported by evidence.
• Have students create a T-chart on chart paper differentiating mass and weight with examples.
• Facilitate a small group activity where learners predict what happens to weight if gravity changes (e.g., traveling to Mars), using calculations to support predictions.

5. Assessment & Reflection (10 minutes)

• Quick quiz (5 questions) focusing on:
  • Definitions of gravity, mass, weight
  • Calculating weight from given mass and gravitational acceleration
  • Real-world application questions (Moon, Mars).
• Exit Ticket: Write one real-life example demonstrating the difference between mass and weight and explain why it matters.

---

Success Criteria

• Students accurately define gravity, mass, and weight.
• Students correctly calculate weight using the given equation.
• Students explain the difference between mass and weight and justify how gravity influences weight.
• Ability to apply concepts to solve problems involving different gravitational environments.

---

Differentiation Strategies

Learner Type	Strategy
Visual learners	Use diagrams, video clips, and physical demonstrations with spring scales and masses.
Kinesthetic learners	Hands-on measurement activity with real objects and scales to feel weight differences.
English Language Learners	Use simplified language, paired discussion, and vocabulary charts with visuals.
Students with IEPs	Provide step-by-step instructions, additional scaffolding during calculations, and extra time. Use peer buddies.
Advanced learners	Give extension problems involving weight in different planetary gravities and conceptual questions about gravity in space.

---

Extension Activities

• Research project: Investigate and present how gravity varies on different planets and how it would affect astronauts or space missions.
• STEM challenge: Design an experiment to test the effect of gravity on pendulum motion using different masses.
• Write a creative story from the perspective of an astronaut describing how changes in gravity affect their daily life.

---

Teacher Notes

• Ensure that during measurements, students handle equipment carefully and collaborate effectively.
• Emphasize accurate use of units (kg for mass, newtons for weight).
• Draw connections to prior knowledge of forces and motion from previous lessons.
• Use formative questioning throughout to gauge understanding and address misconceptions immediately.

---

This lesson is designed to make gravity, mass, and weight tangible and clear for middle school students, encouraging critical thinking and real-world connection, all while meeting Common Core and NGSS standards.