Grade 10 physics – Pressure Quiz
1. What is the definition of pressure?
Pressure is defined as the normal force acting on a surface divided by the area of that surface (p = F/A).
2. What is the SI unit of pressure?
The SI unit of pressure is the pascal (Pa). 1 Pa = 1 N/m².
3. If you press a thumbtack into a wall, why does the point pierce the wall more easily than the blunt end?
Pressure increases when the force acts on a smaller area. The sharp point concentrates the force, producing higher pressure that pierces the wall.
4. Which of these statements about pressure in a liquid is true?
Hydrostatic pressure increases with depth according to p = p0 + ρgh, so deeper points have greater pressure.
5. Which expression gives the increase in pressure in a liquid due to a depth h below the surface?
The hydrostatic pressure contribution from a column of liquid of depth h is ρgh.
6. If two containers of different shapes are connected and filled with the same liquid, what is true about the pressure at the same level in both containers?
In connected vessels with the same fluid, pressure at the same horizontal level is equal regardless of the vessel shape (hydrostatic principle).
7. What does Pascal's principle state about pressure in a confined fluid?
Pascal's principle says that any applied pressure change in an enclosed fluid is transmitted equally throughout the fluid, which is the basis of hydraulic machines.
8. A small piston of area 0.02 m² is pushed with a force of 100 N in a hydraulic system. If the large piston has area 0.5 m², what upward force does the large piston produce (assuming ideal fluid)?
Pressure is the same: p = 100 N / 0.02 m² = 5000 Pa. Force on large piston = p × 0.5 m² = 5000 × 0.5 = 2500 N.
9. Atmospheric pressure at sea level is about:
Standard atmospheric pressure at sea level is approximately 101325 Pa, often rounded to 101300 Pa or 101.3 kPa.
10. Which instrument is commonly used to measure atmospheric pressure?
A barometer measures atmospheric pressure, often using a mercury column or an aneroid capsule.
11. Why does a suction pump work when you draw water up by lowering the pressure above it?
Reducing pressure above the water creates a pressure difference; atmospheric pressure on the reservoir pushes the water up into the lower-pressure area.
12. If a U-tube manometer shows a difference in liquid column height h, the pressure difference between the two sides equals:
The pressure difference supported by a column of liquid of height h is given by ρgh.
13. Which of these affects the hydrostatic pressure at a point inside a liquid?
Hydrostatic pressure at a point depends on depth and density (p = p0 + ρgh), not on container shape or liquid colour.
14. A closed container holds a gas and the temperature increases while volume stays constant. What happens to the gas pressure inside the container?
At constant volume, increasing temperature raises the average kinetic energy of gas molecules, increasing collision frequency and pressure (Gay-Lussac’s law).
15. Which of these statements explains why a wide flat shoe causes less damage to soft ground than a sharp high heel?
Lower pressure from a larger contact area reduces sinking and damage to soft ground.
16. Convert 2.5 kPa to pascals.
1 kPa = 1000 Pa, so 2.5 kPa = 2.5 × 1000 = 2500 Pa.
17. Why does a swimmer feel more pressure on their ears as they dive deeper underwater?
Hydrostatic pressure increases with depth (p increases by ρgh), so deeper water exerts greater pressure on the swimmer.
18. A column of mercury 760 mm high balances atmospheric pressure. If water is used instead of mercury, approximately how high would the water column be (density of water ≈ 1000 kg/m³, mercury ≈ 13600 kg/m³)?
Pressure is ρgh. For same pressure, h_water = h_Hg × (ρ_Hg/ρ_water) ≈ 0.760 m × (13600/1000) ≈ 10.3 m.
19. A tyre gauge shows the internal pressure of a car tyre as 220 kPa. This reading is most likely the pressure:
Tyre gauges usually show gauge pressure, the pressure above atmospheric pressure, measured in kPa.
20. If you cut a block into two pieces and apply the same force to the same face area on one piece, how does the pressure compare with the original block?
Pressure depends only on the force and area at the contact point (p = F/A); cutting the block does not change p if F and A are unchanged.
21. Which of these best describes why a gas exerts pressure on the walls of its container?
Gas pressure results from many molecular collisions with container walls, each transferring momentum and producing a force per unit area.
22. A boat floats because of buoyancy. Which pressure-related reason explains this?
Hydrostatic pressure increases with depth, so the pressure under the hull is higher than above, creating a net upward buoyant force.
23. In a laboratory, you apply the same force to two pistons of different areas in a closed fluid. If the small piston has area one-quarter of the larger one, how do the forces on the two pistons compare?
With equal pressure transmitted, force on a piston = pressure × area. If the large piston area is four times the small one, its force is four times larger.
24. Which unit is equivalent to 1 pascal?
By definition, 1 pascal equals one newton of force applied uniformly over one square metre (1 Pa = 1 N/m²).
25. When you squeeze a closed plastic bottle and release it quickly, air rushes back in. This happens because:
Squeezing and releasing changes internal pressure; when internal pressure is temporarily below atmospheric, outside air moves in to equalize the pressure.
26. During a practical, a pupil measures a force of 20 N acting on a plate of area 0.5 m². What is the pressure on the plate?
Pressure p = F/A = 20 N / 0.5 m² = 40 N/m² = 40 Pa.
27. Which of the following is NOT a factor that affects pressure at a given depth in a liquid?
Hydrostatic pressure depends on depth and density (and any layers above), but not on the container's shape.
28. What is the definition of pressure in physics?
Pressure is defined as the force acting perpendicular to a surface divided by the area of that surface (P = F/A), measured in pascals (N/m²).
29. A force of 200 N acts uniformly on an area of 0.5 m². What is the pressure?
Use P = F/A = 200 N / 0.5 m² = 400 N/m² = 400 Pa.
30. Which unit is equivalent to one pascal (Pa)?
A pascal is defined as one newton of force applied uniformly over an area of one square metre (1 Pa = 1 N/m²).
31. How does pressure in a fluid change with depth?
Fluid pressure increases with depth according to P = P0 + ρgh because the weight of the fluid above adds to the pressure.
32. What is the pressure due to a 2 m column of water (density 1000 kg/m³), neglecting atmospheric pressure? (Take g = 10 N/kg)
Use P = ρgh = 1000 kg/m³ × 10 N/kg × 2 m = 20,000 N/m² = 20,000 Pa.
33. Which of these statements about atmospheric pressure at sea level is closest to the actual average value?
Standard atmospheric pressure at sea level is approximately 101,325 Pa, often approximated as 101 kPa.
34. Two identical blocks are pressed with the same force, one has a larger area of contact than the other. Which block experiences the larger pressure?
Pressure P = F/A; with the same force, a smaller contact area gives a larger pressure.
35. Why can a needle penetrate the skin more easily than a blunt object when the same force is applied?
The sharp needle concentrates the force on a tiny area, giving much higher pressure that breaks the skin more easily.
36. A hydraulic jack uses a small piston area of 0.01 m² and a large piston area of 0.5 m². If a force of 100 N is applied to the small piston, what ideal upward force appears on the large piston (neglecting losses)?
Pascal's principle: pressure transmitted equally. Pressure = 100 N / 0.01 m² = 10,000 Pa. Force on large piston = 10,000 Pa × 0.5 m² = 5,000 N.
37. Which formula gives the pressure at depth h in a liquid with density ρ under atmosphere?
Absolute pressure at depth equals external atmospheric pressure plus the hydrostatic pressure from the liquid column: P = P_atm + ρgh.
38. A closed container shows a gauge pressure of 200 kPa. If atmospheric pressure is 100 kPa, what is the absolute pressure inside the container?
Absolute pressure = atmospheric pressure + gauge pressure = 100 kPa + 200 kPa = 300 kPa.
39. If two points in the same horizontal plane in a fluid are at equal depth, how do their pressures compare?
At the same depth in a continuous fluid and same fluid, hydrostatic pressure is the same regardless of horizontal position.
40. Which instrument is used to measure atmospheric pressure?
A barometer measures atmospheric pressure; a common type is the mercury barometer.
41. Why does pressure inside a pressure cooker increase when heated?
Heating converts water to steam and increases temperature; more gas particles with higher kinetic energy in the fixed volume raise the pressure (ideal gas behaviour).
42. A tyre has a pressure of 200 kPa (gauge). If atmospheric pressure is 100 kPa, what is the force exerted by the air on 0.03 m² of tyre area inside (use absolute pressure)?
Absolute pressure = 100 kPa + 200 kPa = 300 kPa = 300,000 Pa. Force = P×A = 300,000 Pa × 0.03 m² = 9,000 N.
43. Which of the following does NOT affect the hydrostatic pressure at a given depth in a liquid?
Hydrostatic pressure at a depth depends on density, depth and gravity (P = P0 + ρgh), not on how much liquid is in the container provided depth is unchanged.
44. Why does a dam need to be thicker at the bottom than at the top?
Hydrostatic pressure increases with depth (ρgh), so the base of a dam must resist larger lateral forces and is therefore made thicker.
45. A block floats in a liquid. The pressure under the part of the block in contact with the liquid is related to:
Local fluid pressure under the block depends on depth (ρgh) and atmospheric pressure; buoyant force depends on displaced volume, but local pressure is depth-dependent.
46. Which is an effect of increasing temperature on the pressure of a fixed mass of gas in a sealed rigid container?
For a fixed volume, increasing temperature raises the average kinetic energy of gas molecules, causing more frequent and forceful impacts on the walls and increasing pressure (Gay-Lussac's law behaviour).
47. What is gauge pressure?
Gauge pressure is the pressure above (or below) atmospheric pressure; absolute pressure equals gauge pressure plus atmospheric pressure.
48. A rectangular box contains mercury (density 13,600 kg/m³) to a depth of 0.1 m. What is the hydrostatic pressure at the bottom due to mercury alone? (g = 9.8 m/s²)
P = ρgh = 13,600 kg/m³ × 9.8 m/s² × 0.1 m = 13,328 N/m² ≈ 13,328 Pa.
49. Which principle explains why pressure applied to a confined fluid is transmitted equally in all directions?
Pascal's principle states that a pressure change applied to an enclosed fluid is transmitted undiminished to every part of the fluid and the walls of its container.
50. If you dive deeper into a lake, why do your ears feel a difference?
As depth increases, water pressure increases (ρgh) and the higher external pressure affects air spaces in the ear; equalising by swallowing helps.
51. A cube with top surface area 0.04 m² experiences a downward force of 80 N on its top face. What pressure acts on the top face?
P = F/A = 80 N / 0.04 m² = 2,000 N/m² = 2,000 Pa.
52. Why does air pressure decrease as you climb a mountain?
Atmospheric pressure at a point equals the weight of the air column above that point; climbing reduces the column height so less weight and lower pressure.
53. In a container of connected vessels with different shapes but same liquid level, why do the pressures at the bottom of each branch compare?
Communicating vessels show that pressure at a given depth in the same fluid is the same regardless of the vessel shape; liquid levels adjust to equalise pressure.