Understanding Gravity

Overview

Unit Title: Forces in Motion
Lesson Title: Understanding Gravity
Year Level: Year 7
Subject: Science
Duration: 45 minutes
Class Size: 20 students

Alignment to the Australian Curriculum

Curriculum Area:

• Science Understanding – Physical sciences

Content Description (ACSSU117):

• Change to an object’s motion is caused by unbalanced forces, including Earth’s gravitational attraction, acting on the object.

General Capabilities:

• Critical and creative thinking
• Literacy
• Numeracy
• Science inquiry skills

Lesson Intentions

By the end of this lesson, students should be able to:

• Describe gravity as a force that pulls objects towards the centre of the Earth.
• Explain that the magnitude of gravitational force depends on the mass of the object.
• Predict and observe the effect of gravity through experimental investigation.

Success Criteria

Students will:

• Correctly define gravity in their own words.
• Participate actively in experiments and accurately record observations.
• Make reasoned conclusions about the relationship between mass and gravitational pull.

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Materials Required

• 10 small rubber balls
• 10 larger basketballs
• Spring scales (one per group)
• Stopwatches
• Worksheets for recording predictions and observations
• Access to an open area (courtyard or hall)
• Whiteboard and markers

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Key Vocabulary

• Gravity
• Mass
• Force
• Weight
• Acceleration

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Lesson Sequence

1. Introduction (10 minutes)

"Gravity in Action" Brainstorm

• Open with a quick class brainstorm. Pose the question:
  🧠 "What would happen if gravity suddenly turned off?"
• Encourage ‘out-of-the-box’ thinking; scribe students' imaginative ideas on the board.
• Transition by explaining that today they will learn how gravity works every moment of every day.

Explicit Teaching Moment

• Define gravity:
  Gravity is the invisible force that pulls everything towards the Earth’s centre.
• Link to students’ experiences: standing on the ground, objects falling, throwing a ball.

2. Investigation Setup (5 minutes)

• Explain the main experiment:
  Students will explore if different masses fall differently due to gravity.
• Put students into groups of four (pre-assigned for diversity).
• Distribute materials to each group: small balls, basketballs, spring scales, and worksheets.

Safety Note: Remind students to be aware of their surroundings when dropping basketballs.

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3. Experiments (20 minutes)

Part A: Observing Fall Times (10 minutes)

Activity Instructions:

• One group member drops a rubber ball and a basketball simultaneously from shoulder height.
• Another group member uses a stopwatch to time how long it takes each ball to hit the ground.
• Repeat three times for accuracy.

Key Question:

• Do heavier objects fall faster than lighter objects?

Expected Observations:

• Both objects land at the same time — prompting discussion about mass and gravitational acceleration.

Part B: Measuring Weight (10 minutes)

Activity Instructions:

• Use the spring scales to measure the force (weight) required to hold the small ball and the basketball.
• Record the measurements on the worksheet.

Key Question:

• Does mass affect the gravitational force (weight)?

Expected Observations:

• Heavier objects show a higher reading on the spring scale, illustrating that more mass equals a stronger gravitational pull.

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4. Class Discussion and Reflection (8 minutes)

Gather students for a whole-class discussion:

Prompting Questions:

• What did you notice about the time it took objects to fall?
• Was this different from what you expected?
• How did mass affect the force you measured?

Summarise key points clearly on the Whiteboard:

• Gravity pulls all objects down equally regardless of mass.
• Heavier objects feel more gravitational force but fall at the same speed.

Anchor learning by connecting back to common experiences — such as why astronauts ‘float’ on the Moon (less gravitational pull!).

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5. Exit Ticket (2 minutes)

Each student must complete an "Exit Ticket":
▶ One thing I learned about gravity today is...
▶ One question I still have about gravity is...

Teacher collects exit tickets at the door to gauge understanding and inform tomorrow’s lesson.

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Differentiation

Support:

• Provide scaffolded worksheets with sentence starters.
• Pair EAL/D students with supportive peers.

Extension:

• Challenge fast finishers:
  ➡ Predict what would happen to gravity on planets larger or smaller than Earth.
  ➡ Sketch a quick scientific poster explaining gravity for Year 4 students.

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Assessment

Formative Assessment:

• Observation during experiments and group discussions.
• Worksheet accuracy (data collection and basic analysis).
• Exit ticket responses will identify individual student understanding and misconceptions.

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Teacher Reflection (Post-Lesson)

• Were students able to articulate how mass affects gravitational force but not falling time?
• Did students engage meaningfully with both parts of the investigation?
• Plan to incorporate any lingering questions into Lesson 3: "Exploring Balanced and Unbalanced Forces".

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Additional Teacher Notes

• Consider using real-world examples from Australian life — dropping objects on the footpath vs. at Bondi Beach or Uluru — to localise and personalise learning.
• If possible, integrate Aboriginal and Torres Strait Islander perspectives on the relationship between Earth and forces of nature in later lessons for broader cultural inclusivity.

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