Short Answer Questions on Pressure – Click to Reveal Answers
🧪 Pressure – Short Answer Type Questions (Click to Reveal Answers)
1. What is meant by pressure? State its S.I. unit.
Pressure is the force acting per unit area. SI unit: pascal (Pa).
2. Differentiate between thrust and pressure.
Thrust is the total force acting perpendicular to a surface. Pressure is Thrust per unit Area.
Thrust has unit newton, Pressure has unit pascal
.
3. How does pressure depend on area? Give an example.
Pressure is inversely proportional to area. A sharp knife cuts better due to higher pressure on small area.
4. Why is the tip of a pin made sharp?
To apply more pressure on a small area, making it easier to pierce objects.
5. Explain:
(a) It is easier to cut with a sharp knife.
(b) Sleepers are laid under railway tracks.
(a) A sharp knife exerts more pressure due to smaller area.
(b) Sleepers distribute the weight and reduce pressure on tracks.
6. What is meant by fluid pressure?
The pressure exerted by a fluid (liquid or gas) in all directions on the walls of the container or any object in it.
7. How does pressure by solids and fluids differ?
Solids exert pressure only on the surface in contact. Fluids exert pressure in all directions.
8. Name three factors on which pressure at a point in a liquid depends.
Depth, density of liquid, and acceleration due to gravity.
9. Give the expression for pressure in a liquid and explain terms.
P = hρg; where h = depth, ρ = density of liquid, g = acceleration due to gravity.
10. How does pressure at the same depth differ in sea vs river water?
Sea water has higher density due to salts, so it exerts more pressure than river water at same depth.
11. Why does a gas bubble grow in size as it rises in a lake?
Pressure decreases as the bubble rises, so it expands to balance the reduced external pressure.
12. Why are dam walls broader at the bottom?
Water pressure increases with depth, so thicker walls are needed to withstand more pressure at the bottom.
13. Why do sea divers need special suits?
To protect them from high water pressure at great depths which can harm the body.
14. State the laws of liquid pressure.
Pressure in a liquid: (i) increases with depth, (ii) is same in all directions at same depth, (iii) depends on density of liquid.
15. Observation when holes A and B are made at different heights in a water cylinder?
Water from hole A (lower) flows out with more force due to higher pressure at greater depth.
16. Principle of hydraulic press and its use.
Works on Pascal’s Law: pressure is transmitted equally in all directions in a fluid. Used in car lifts, juice machines, etc.
