Forces and Gravity: Air Resistance — Year 5 Lesson Plan
National Curriculum: Science — Forces, Year 5: identify the effects of air resistance; notes and guidance: falling objects, parachutes and sycamore seeds; designing parachutes and fair testing
Overview
The second of five Forces and Gravity lessons. Pupils learn that air resistance is a force that pushes against objects moving through air and slows them down. They observe falling paper, cupcake cases and sycamore seeds, then plan and carry out a fair test to find out how the size of a parachute affects how quickly it falls.
Forces and Gravity: Air Resistance learning objectives
- Explain that air resistance is a force that acts against objects moving through air.
- Describe how a larger surface area increases air resistance.
- Plan a fair test, changing one variable and keeping the others the same.
- Use results to explain which parachute design falls most slowly.
Success criteria
- I can explain what air resistance is and which way it acts.
- I can explain why a bigger parachute falls more slowly.
- I can say what I changed, measured and kept the same in my fair test.
- I can use my results to write a conclusion.
Key Vocabulary
Suggested Lesson Structure
Revisit the end of lesson 1: drop a flat sheet of paper and a crumpled sheet together. They have the same weight, so why does the crumpled one land first? Then drop a single cupcake case and a sycamore seed (or a paper spinner). Pupils describe how each falls.
Explain that as an object falls it pushes air out of the way, and the air pushes back. This force is air resistance; it acts in the opposite direction to the movement. Draw force arrows on a falling parachute: gravity pulling down, air resistance pushing up. The bigger the surface pushing against the air, the more air resistance, so the slower it falls. Link to real life: skydivers, sycamore seeds, streamlined cyclists and cars that want less air resistance.
Fair test: groups make parachutes from squares of plastic bag with sides of 10 cm, 20 cm and 30 cm, using the same string and the same weight (such as a lump of plasticine). They agree what to change (canopy size), what to measure (time to fall, with a stopwatch) and what to keep the same (drop height, weight, string). Each parachute is dropped three times from the same height and the times are recorded.
Pupils work out the average time for each parachute, write a conclusion (“The bigger the canopy, the …”) and explain it using the words gravity and air resistance. Challenge: suggest why we repeat each drop three times.
Show a skydiver before and after opening a parachute. Ask: what changes when the parachute opens? Pupils explain using the words air resistance and surface area.
Support and extension for forces and gravity: air resistance
Support
- Give a planning board with three columns: change, measure, keep the same, with picture cues.
- Provide a partly completed results table with the parachute sizes filled in.
- Pair pupils so one drops and one times, then swap.
Extension
- Plan a second test changing the shape of the canopy instead of its size.
- Explain why repeating each drop three times makes the results more reliable.
- Find out how a sycamore seed's shape helps it travel away from its parent tree.
Check for understanding
Quick questions for the plenary or an exit ticket. Tap a question to see the answer.
1. Which way does air resistance push on a falling parachute?
Answer: Upwards, against the direction it is moving.
2. Why does a bigger parachute fall more slowly?
Answer: It has a bigger surface area, so there is more air resistance.
3. In the parachute test, what should stay the same?
Answer: The drop height, the weight and the string (everything except the canopy size).
4. Why does a crumpled sheet of paper fall faster than a flat one?
Answer: It has a smaller surface area, so less air resistance.
Resources you will need
- Plastic bags cut into 10 cm, 20 cm and 30 cm squares
- String, sticky tape and plasticine or paper clips for the weight
- Stopwatches
- Cupcake cases and sycamore seeds or paper spinners
- A safe place to drop from (a teacher holds the parachute at a fixed height)
Common Misconceptions
- Air resistance only acts on parachutes. It acts on everything moving through air, including people, balls and cars.
- Air resistance pulls objects up. It pushes against the direction of movement, so for a falling object it pushes upwards.
- A parachute stops gravity. Gravity still pulls down; the parachute increases air resistance so the fall is slower.
- Changing two things at once still gives a fair result. Only one variable can change in a fair test.
Prior Knowledge
Pupils should already be able to:
- Know that gravity pulls unsupported objects towards the Earth (lesson 1).
- Draw simple force arrows (lesson 1).
- Use a stopwatch and record results in a table.
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