Lesson: Gravity

Year: 5 | Subject: Science | Time Allocation: 100%

Class/Set: ____________ Date/Term: ____________

LO (WALT): To explain that unsupported objects fall towards the Earth because of the force of gravity.

Success Criteria (WILF):

1. I can define gravity as a pull force that acts towards the centre of the Earth.
2. I can distinguish between mass (measured in kg) and weight (measured in Newtons).
3. I can accurately use a Newton meter to measure the gravitational pull on various objects.

1. Starter (15%)

• Demonstrate: Hold a heavy textbook and a single sheet of paper at the same height.
• Ask: "If I release these at the exact same time, what will happen and why?"
• Discuss: Facilitate a brief partner talk regarding the "invisible force" at work.
• Recall: Prompt students to remember the names of other forces studied (e.g., friction, magnetism) to activate prior knowledge.

2. Main Activity (70%)

Teacher Input:

• Explain: Introduce Sir Isaac Newton and the historical context of his observations regarding falling objects.
• Define: Clarify the distinction between 'Mass' (the amount of matter in an object, measured in grams/kilograms) and 'Weight' (the measure of the force of gravity pulling on that mass, measured in Newtons).
• Model: Show the class a Newton meter (force meter). Demonstrate: how to zero the scale and hang an object safely to read the measurement.
• Identify: Point out that on Earth, a mass of 100g has a weight of approximately 1 Newton (1N).

Student Task:

• Investigate: Students work in small groups to select five classroom objects (e.g., a pencil case, a shoe, a glue stick).
• Estimate: Record an estimate of the weight in Newtons (N) before measuring.

Object	Mass (g/kg)	Est. Weight (N)	Actual Weight (N)
Glue Stick	40g	0.5N	0.4N
Reading Book	250g	3.0N	2.5N
Pencil Case	150g	2.0N	1.5N

• Analyze: Students must write one sentence for each object comparing their estimate to the actual result using the Tier 2 vocabulary: 'accurate', 'significant', or 'proportional'.
• Challenge: "If we took these objects to the Moon, where gravity is weaker, which column in our table would change and which would stay the same?"

3. Plenary (15%)

• Review: Use a 'Hinge Question': "If gravity is a pull towards the centre of the Earth, why don't we fall through the floor?" (Expectation: Support force/Normal contact force).
• Reflect: Ask students to summarise the 'Golden Rule' of gravity in exactly ten words.

4. Resources

• Newton meters (force meters) - various scales (0-10N, 0-50N).
• Selection of classroom objects.
• Digital scales (to check mass in grams).
• Images of Sir Isaac Newton and the Moon's surface for visual scaffolding.

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⚠ TEACHER’S GUIDANCE

💡 Pedagogical Pulse

• Delivery Advice: For Year 5, the distinction between mass and weight is a significant conceptual hurdle. Avoid using the terms interchangeably during the lesson. Consistently refer to "Weight" when using the Newton meters and "Mass" when using the scales.
• Misconception Alert: Students often believe that heavy objects fall faster than light objects. While air resistance affects a flat sheet of paper, in a vacuum (or with aerodynamically similar objects), they fall at the same rate. Use a crumpled piece of paper vs a flat sheet to demonstrate air resistance if this arises.
• Safety & Nuance Check: Ensure Newton meters are not over-stretched beyond their scale limit, as this damages the internal spring and leads to inaccurate results.

🔑 Task Solutions and Mirror-Labeling

• Task: Estimation and Measurement Table:

  • Glue Stick: ~0.4N
  • Reading Book: ~2.5N (depending on thickness)
  • Pencil Case: ~1.5N to 2.0N
  • Note: Ensure students are reading the 'N' scale, not the 'g' scale often found on the opposite side of the meter.

• Challenge Answer: Mass vs Weight on the Moon:

  • The Mass would stay the same (the object is still made of the same amount of 'stuff').
  • The Actual Weight would change (it would be roughly 1/6th of the Earth weight) because the gravitational pull is weaker.

• Hinge Question Answer:

  • We don't fall through the floor because the floor pushes back with an equal and opposite force (Support force/Normal contact force). Gravity pulls us down, but the solid structure of the floor prevents the movement.