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| Focus: Explain buoyancy and flotation in three situations. | ||||||
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Questions / instructions: |
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%
responses
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GEd
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MI
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1. Imagine that you have a ball of plasticine. You put it in water and it sinks. Then you shape it into a boat. Now it floats. Why did the ball of plasticine sink but the boat float? Tënä me pohewa noa he poi kerepëhi [ball of plasticine] täu. Ka kuhuna e koe ki röto i te wai, ka totohu. Kia hangaia e koe hei waka, kätahi ka mänu. He aha te poi kerepëhi i totohu ai, i mänu kë ai ko te waka? |
0
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0
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boat
shape displaces enough water to hold weight of plasticine
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more
spread out so it floats/ water holds it up there
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4
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5
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because
there is air inside it.
|
29
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11
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2. Why do things feel lighter when you pick them up under water? He aha i mämä ake ai he mea ka hikina ana mai i raro i te wai? |
2
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5
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some
of the weight is supported by the water displaced
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because
water is less dense than air
|
1
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2
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there
is less or no gravity under water
|
21
|
13
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3. Someone holds the ball at the bottom. Why does it jump out of the water when they let it go? Ka pupuritia e tëtahi te poi ki raro. Kia tukua, nä te aha i peke ake ai te poi? |
1
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0
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Under
the water: ball weighs less than the water displaced
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air
in the ball makes it rise
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43
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36
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Above
the water: ball moves upward because of inertia
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0
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0
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ball
is going fast when it reaches the surface
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3
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0
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| Commentary:
This was a difficult task beyond the reach of most year 8 students. There was not a statistically significant difference between GEd (General Education) and MI (Mäori Immersion) students. |
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