Fluids Basics
Q: What two states of matter count as fluids?
A: Liquids and gases.
Q: What is the formula for pressure?
A: Pressure = Force ÷ Area.
What happens to pressure as depth increases?
Answer: Pressure increases.
What is the formula for density?
Answer: Density = Mass ÷ Volume
A force of 20 N is applied to an area of 4 m². What is the pressure?
Answer: 20 ÷ 4 = 5 Pa
Q: What does it mean for a fluid to “take the shape of its container”?
A: It changes shape to match the container because its particles move freely.
Q: If force increases and area stays the same, what happens to pressure?
A: Pressure increases.
Why is water pressure greater than air pressure at the same depth?
Answer: Water is denser than air.
If an object is less dense than water, what happens?
Answer: It floats.
Find the density: mass = 30 g, volume = 10 cm³.
Answer: 30 ÷ 10 = 3 g/cm³
Q: Name one liquid and one gas that are considered fluids.
A: Example: Water (liquid), Air (gas).
Q: Why does pressing your finger on a desk hurt more than pressing your whole hand?
A: Smaller area → higher pressure.
Where is atmospheric pressure highest: mountaintop or sea level?
Answer: Sea level.
Why does oil float on water?
Answer: Oil is less dense than water.
A diver at 10 meters experiences greater pressure because water has more ______ than air.
Density
Q: What key feature makes gases different from liquids?
A: Gases change volume; liquids keep a constant volume.
Q: Why do fluids push in all directions?
A: Because particles collide with surfaces from all sides.
Why do divers feel pressure increase rapidly as they go deeper?
Answer: More water above them adds weight, increasing pressure.
Two objects have the same volume, but one has more mass. Which has the higher density?
Answer: The one with more mass.
A force of 50 N is applied to an area of 2 m². What is the pressure? What happens if the area doubles?
Answer:
Pressure = 25 Pa
If area doubles → pressure decreases
Q: Why can both gases and liquids flow?
A: Their particles are not tightly packed and can move past one another.
Q: Why does a sharp knife cut better than a dull knife?
A: Because a sharp knife has a smaller surface area, creating higher pressure when the same force is applied.
Why is atmospheric pressure lower on a mountain?
Answer: There is less air above you.
Why do denser materials sink below less dense materials?
Answer: Because they have more mass packed into the same amount of space.
Object A: mass = 40 g, volume = 20 cm³
Object B: mass = 20 g, volume = 20 cm³
Which is denser, and will each sink or float?
Answer:
Object A density = 2 g/cm³ → sinks
Object B density = 1 g/cm³ → floats (same as water)