Year 5 · Autumn 1.1 · Step 7

Earth & Space

Investigate — water resistance

Carrying out the comparative test: keep the clay mass equal, change the shape, time the sink.

Arrival Starter I do We do Independent Exit ticket
🌱 Seedling · Working towards 🌿 Sapling · Expected 🌳 Oak · Greater depth

⏱ Whole lesson ≈ 44 min · pick a tier in the bar, or leave on "All"

Arrival 4 min

Recap of last lesson: the water-resistance plan.

Recap: our water plan

🌱 Seedling
Working towards

We change the ____ and measure the ____.

🌿 Sapling
Expected
  1. Name our independent variable.
  2. Name one controlled variable.
  3. Predict the fastest shape.
🌳 Oak
Greater depth

Why might we repeat each shape and remove any anomalous result before concluding?

Bridge into todayPlan ready. Today we carry out the water-resistance test and draw a conclusion.
Starter 5 min

Set up: same clay mass, same cylinder, same water.

Fair test in water

Keep the mass of clay the same for each shape. Drop from the same point at the top of the water. Time to the bottom in parts of a second, and repeat.

🌱 Seedling
Working towards

What must stay the same? Circle: mass · shape · cylinder

🌿 Sapling
Expected

Why keep the mass of clay the same for every shape?

🌳 Oak
Greater depth

Why repeat each shape? What does averaging protect against?

I do · 1 6 min

Teacher models a clean drop and recording, then watch.

Run the water test

▶ Can't see it? Watch "Water resistance — Year 5 Forces" on YouTube

Swap the clip: change the ID after /embed/ (now sZquDi8aomw).

Say thisLower each shape to the same start point, release and time to the bottom. The most streamlined shape has the least water resistance, so it should reach the bottom first. Repeat and average.
⚖️
Same massclay kept equal
⏱️
Time to bottomparts of a second
🔁
Repeatthen average
We do · 1 6 min

Record results and read the pattern together.

Record and compare

Shape | Try 1 | Try 2 | Try 3 | Average time to bottom (s)

What we expect
Streamlined → shortest time.   Blunt → longest time.
More streamlined means less water resistance, so a faster sink.
I do · 2 4 min

Play the animation. Bust: water resistance needs water / isn't friction.

Shape decides the speed

bottom streamlined blunt same mass of clay, different shapes

Same mass of clay, different shapes — the streamlined one reaches the bottom first.

Model the ruleWater resistance is a friction force — the water slows the object down. It happens in any liquid, not just water. Because the mass is the same, only the shape changes the result.

Watch for: "water resistance isn't friction" and "it only happens in water".

We do · 2 5 min

Decide what would spoil the water test.

Fair or spoiled?

Decide together
"Use the same mass of clay each time."   "Swap to a different liquid halfway."   "Repeat each shape three times."
Which keep it reliable, and which would spoil it?
Independent 10 min

On your own. Sort each action, then run and conclude at your tier.

Reliable water test sorter

✅ Makes results reliable

⚠️ Would spoil the results

🚫 Myth to bust

Tap a card to sort it…

🌱 Seedling
Working towards

Sort the cards, then record your times in the table.

🌿 Sapling
Expected

Sort them, then write a conclusion: which shape had the least water resistance?

🌳 Oak
Greater depth

Sort them, then explain your conclusion and suggest one way to extend the test.

Exit ticket 4 min

Answer at your tier, then hand it in.

Show what you know

🌱 Seedling
Working towards
  • Which shape sank fastest?
  • Water resistance is a type of ____.
🌿 Sapling
Expected
  • Why is water resistance a friction force?
  • Why keep the clay mass the same?
🌳 Oak
Greater depth

Does water resistance need water? Explain, and give one way to extend the test.

TA Focus · Running the water test
Same-mass clay is the make-or-break control. Streamlined should reach the bottom first. For the sorter, ask 'reliable, or would it spoil the test?' The myths are 'water resistance isn't friction' and 'it only happens in water'.
Cold Call · Question bank
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