Density and pressure
Grade 9: density = mass / volume, why things float or sink, pressure = force / area, pressure in liquids increases with depth, air pressure.
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Questions
Which formula gives density?
- force ÷ area
- mass × volume
- mass ÷ volume
- volume ÷ mass
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mass ÷ volumeA block has a mass of 200 g and a volume of 50 cm³. What is its density?
- 0.25 g/cm³
- 10 g/cm³
- 150 g/cm³
- 4 g/cm³
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4 g/cm³A metal has mass 90 g and volume 30 cm³. What is its density in g/cm³? (Answer out loud)
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3 g/cm³Two objects with the same volume but different masses have different densities. (True or false?)
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TrueAn object floats in water when its density is...
- exactly double water's
- less than water's density
- more than water's density
- the same as its mass
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less than water's densityWater has a density of 1 g/cm³. Which material would sink in it?
- Cork, 0.24 g/cm³
- Ice, 0.92 g/cm³
- Iron, 7.9 g/cm³
- Oil, 0.9 g/cm³
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Iron, 7.9 g/cm³A huge steel ship can float because its overall density is less than water's. (True or false?)
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TrueWhich formula gives pressure?
- area ÷ force
- force × area
- force ÷ area
- mass ÷ volume
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force ÷ areaA force of 100 N acts on an area of 4 m². What is the pressure in N/m²? (Answer out loud)
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25 N/m²Why does a sharp knife cut better than a blunt one?
- It has a larger contact area
- It has a larger mass
- Smaller area gives less pressure
- Smaller area gives more pressure
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Smaller area gives more pressureWhy do snowshoes stop you sinking into deep snow?
- They concentrate force on a small area
- They increase the force downward
- They make you lighter
- They spread your weight over a larger area
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They spread your weight over a larger areaAs a diver goes deeper in the sea, the water pressure on them...
- decreases
- drops to zero
- increases
- stays the same
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increasesAt the same depth, water pressure acts only downwards, not sideways. (True or false?)
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FalseWhy are dam walls built thicker at the bottom?
- Water is lighter at the bottom
- Water pressure is greatest at the bottom
- Water pressure is greatest at the top
- Water pressure is the same everywhere
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Water pressure is greatest at the bottomWhat causes air pressure?
- Air particles colliding with surfaces
- Air particles moving away from surfaces
- Air particles sticking to surfaces
- Wind blowing only in storms
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Air particles colliding with surfacesHow does air pressure change as you climb a high mountain? (Answer out loud)
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It gets lower (decreases)
Play it as a game
Fishing PondAnswer right to cast at a buoy: fish worth 1 to 3, the golden fish for 5, or a silly old boot!
Claw MachineAnswer right to work the claw: grab a plush prize, but the big ones slip more often!
Lucky DropAnswer right to drop a ball through the pegs. Every bucket scores, and the golden one is worth 10!
Mini GolfAnswer right to putt! Pick a shot: sink it for 5, or land in the 3, 2 or 1 ring.