Gravitational Potential Energy

Lesson Overview

Curriculum Area: AQA GCSE Physics - Energy (Key Stage 4, Year 9)
Focus: Gravitational potential energy (GPE) - Calculating, understanding key factors, and applying concepts.
Duration: 45 minutes
Class Details: 30 students, mixed ability, Year 9
Objective: By the end of the lesson, students will:

1. Define gravitational potential energy (GPE) and its role in energy transfer.
2. Use the GPE formula (GPE = mgh) to calculate energy.
3. Understand how height, mass, and gravitational field strength affect GPE.
4. Link GPE to real-world applications, such as theme parks and renewable energy.

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Resources Required

• Materials: Whiteboard, markers, GPE calculation worksheet, printed role-play cards (see Activity 3 below).
• Equipment: A small object (e.g., a ball), string, and a metre ruler for demonstration.
• Technology: Interactive whiteboard or projector, pre-loaded with a 3-minute video clip showing different heights and GPE conversions (e.g., roller coasters or bungee jumping).

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Lesson Structure

Starter (0–5 mins): Think and Discuss

1. Hook Question: "Why does a roller coaster speed up when coming down a hill but slow down climbing up?" Pose this to the class.
2. Class Discussion: Prompt students to give quick responses. Encourage them to think in terms of energy and height.
3. Set the Scene: Briefly explain that they’ll learn about gravitational potential energy today and how it helps us understand these kinds of scenarios.

Teacher Tip: Use an enthusiastic tone to draw attention, even acting surprised by their input to create curiosity.

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Main Activity 1 (5–15 mins): GPE Demonstration

Objective: Define GPE and identify key variables.

1. Visual Demonstration Using a Ball:

   • Hold a small ball at shoulder height and then at head height. Ask, "Which position do you think stores more energy?"
   • Drop the ball from shoulder height, then from head height onto a hard surface. Highlight observational differences (e.g., louder sound, higher bounce).
   • Repeat with a heavier object like a book to emphasise the role of mass.

2. Write a Definition Together:
   Facilitate students in crafting a definition of gravitational potential energy (e.g., "Energy stored in an object because of its height in a gravitational field").

3. Mathematical Formula: Explain GPE = mgh

   • m = mass (kg)
   • g = gravitational field strength (N/kg, Earth = 9.8 N/kg)
   • h = height (metres)
     Write this visibly on the board and have students copy it.

4. Check for Understanding: Ask, "What happens to GPE if one of these factors increases?" (Expected response: GPE increases).

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Main Activity 2 (15–30 mins): Paired Problem-Solving

Objective: Calculate GPE values for different scenarios.

1. Real-World Influence: Display a lifted roller coaster image or a wind turbine to illustrate elements affecting GPE.
2. Group Practice: Distribute GPE worksheets (tailored with three levels of difficulty). Problems include calculations like:
   • "An object with a mass of 5 kg is lifted to 10 m above the ground. What is the GPE stored in the object?"
     (Solution: GPE = 5 × 9.8 × 10 = 490 J).
3. Partner Work: Students work in pairs to solve three progressively difficult problems. Encourage peer teaching.
4. Teacher Circulation: Provide support to students who struggle while challenging those who finish quickly with extension questions (e.g., inverted problems like solving for mass or height).

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Main Activity 3 (30–40 mins): Interactive Role-Play

Objective: Relate GPE to real-world applications.

1. Scenario Cards: Distribute prepared role-play cards with scenarios where GPE is important (e.g., a mountain climber, roller coaster engineer, hydroelectric power designer).
2. Small Group Work (6 per group): Teams brainstorm how GPE relates to their character. They write 1–2 sentences explaining the connection, using GPE terminology.
3. Class Feedback: Groups share their explanations with the class. Encourage creativity and use the opportunity to correct and consolidate understanding.

Example Output:

• Roller coaster engineer: "We use GPE to predict how fast the coaster will be at the bottom of a drop, depending on its height and mass."

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Plenary (40–45 mins): Quick Quiz and Reflection

1. Rapid Fire Quiz: Use mini whiteboards or scrap paper to answer true/false questions, e.g.:
   • "Doubling the height would double the GPE of an object." (True)
   • "Mass has no impact on GPE." (False).
2. Reflections: Ask students to write down one fact they learned and one question they still have. Collect responses for assessment.

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Differentiation Strategies

• Support:
  • Provide formulas with clear examples to struggling students.
  • Pair less confident students with peer mentors during paired work.
• Challenge:
  • Ask more capable students to explain the physics behind the calculations.
  • Pose extension questions about energy conversion (e.g., "What happens to GPE as it converts to kinetic energy on a roller coaster?").

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Assessment

• Formative:
  • Monitor responses during discussions.
  • Evaluate accuracy of calculations in paired work.
• Summative:
  • Check answers to classroom quiz and reflections for understanding.

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Homework

Design a theme park ride where GPE plays a major role. Include a short explanation of how GPE changes throughout the ride and a calculation showing examples of energy storage.

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Teacher Reflection

• Were students actively engaged in activities?
• Did all students grasp the core concepts, especially the key variables in the GPE formula?
• What adjustments are needed to address misconceptions for the next lesson?