Forces and Gravity: Water Resistance — Year 5 Lesson Plan
National Curriculum: Science — Forces, Year 5: identify the effects of water resistance; notes and guidance: making and testing boats of different shapes
Overview
The third of five Forces and Gravity lessons. Pupils learn that water resistance is a force that pushes against objects moving through water. They look at streamlined animals and boats, then shape plasticine into different forms and test which moves through water fastest.
Forces and Gravity: Water Resistance learning objectives
- Explain that water resistance is a force that acts against objects moving through water.
- Describe how a streamlined shape reduces water resistance.
- Test how the shape of an object affects how quickly it moves through water.
Success criteria
- I can explain what water resistance is and which way it acts.
- I can describe what makes a shape streamlined.
- I can test how shape affects movement through water.
Key Vocabulary
Suggested Lesson Structure
Ask: is it easier to walk through a swimming pool or across the playground? Why? Show photographs of a shark, a dolphin, a penguin swimming and a duck's body. Pupils describe what the shapes have in common.
Explain that an object moving through water has to push the water out of the way, and the water pushes back. This force is water resistance, and it acts against the direction of movement. Water is much thicker than air, so water resistance is stronger than air resistance at the same speed. A streamlined shape, with a narrow, smooth front, lets water flow around it easily, so there is less water resistance. Show streamlined boat hulls, submarines and swimmers in a diving position.
Groups shape equal lumps of plasticine (the same mass) into a cube, a flat square, a ball and a streamlined torpedo. They drop each into a tall clear tube or measuring cylinder of water and time how long it takes to reach the bottom, repeating each test. Alternatively, pull the shapes along a water-filled guttering channel with a string and a falling weight.
Pupils record their times, order the shapes from fastest to slowest and write a conclusion explaining the results using water resistance and streamlined. Challenge: design the hull of a fast boat, labelling the features that reduce water resistance.
Ask: why do swimmers dive in with their arms stretched in front of them? Why might a rowing boat be long and thin? Pupils answer using today's vocabulary.
Support and extension for forces and gravity: water resistance
Support
- Give templates for the four shapes so pupils can model them accurately.
- Use photographs of fish and boats with the streamlined features labelled.
- Provide a results table with the shapes already drawn in.
Extension
- Compare the shape of a canal boat with a racing kayak and explain the differences.
- Explain why a swimmer's swimming cap and suit help them go faster.
- Design a fair test to find out whether the depth of the water affects the result.
Check for understanding
Quick questions for the plenary or an exit ticket. Tap a question to see the answer.
1. What is water resistance?
Answer: A force that pushes against an object moving through water.
2. What does streamlined mean?
Answer: Shaped with a narrow, smooth front so water or air flows around it easily.
3. Why did each plasticine shape use the same amount of plasticine?
Answer: To keep the test fair, so only the shape changed.
4. Why do sharks and dolphins have streamlined bodies?
Answer: Less water resistance lets them swim faster using less effort.
Resources you will need
- Plasticine, a balance to measure equal amounts
- Tall clear tubes, measuring cylinders or a water channel (guttering)
- Stopwatches and towels
- Photographs of streamlined animals, boats and submarines
Common Misconceptions
- Water resistance only acts on things floating on the surface. It acts on anything moving through water, including things underwater.
- Heavier shapes always sink faster. In a fair test the mass stays the same and only the shape changes; shape makes a big difference.
- Streamlined means pointed at both ends. The key is a narrow, smooth front so the water flows around it.
- Air resistance and water resistance are completely different forces. They are the same kind of force; water resistance is stronger because water is thicker than air.
Prior Knowledge
Pupils should already be able to:
- Know that air resistance acts against moving objects and depends on shape and surface area (lesson 2).
- Plan a fair test, changing one variable (lesson 2).
- Use a stopwatch and work out an average.
Make it yours
Want a personalised version of this lesson?
Use Staffroom to generate a complete lesson plan tailored to your class — add context about ability, recent learning, or specific pupils and get a plan ready to teach. Free plan, no card required.