A. Choose the correct option
- Pressure can be defined as
a. Force per volume
b. Force per capacity
c. Force per unit area
d. Twice the force
Answer: c. Force per unit area - An open-tube manometer is used to measure
a. Force
b. Length
c. Pressure
d. Volume
Answer: c. Pressure - Deep-sea divers use a special suit to
a. Increase the surface area
b. Protect themselves from high pressures experienced deep underwater
c. Swim faster
d. Make themselves lighter
Answer: b. Protect themselves from high pressures experienced deep under water - When we immerse one end of a drinking straw in a liquid and suck at the other end, we create a
a. Low pressure area in the liquid
b. Low pressure area inside the straw
c. High pressure area inside the liquid
d. High pressure area inside the straw
Answer: b. Low pressure area inside the straw - Inside a vacuum cleaner, there is a fan that makes the pressure inside
a. Lower than the atmospheric pressure outside
b. Higher than the atmospheric pressure outside
c. Equal to the atmospheric pressure outside
d. Blow away the dust particles outside
Answer: a. Lower than the atmospheric pressure outside
B. Fill in the blanks with the correct words
- One pascal is the pressure produced when a force of one newton acts over an area of one square metre.
- Increasing the applied force over the same area increases the pressure produced.
- Liquids and gases are together referred to as fluids.
- A balloon expands when air is blown into it because of the pressure of the air inside.
- In a liquid, pressure increases with depth.
C. Match the following
| Column A | Column B |
| 1. A device used to measure pressure | a. Pascal |
| 2. Pressure due to the weight of the air above | b. Walls of a dam |
| 3. Unit of pressure | c. All directions |
| 4. Atmospheric pressure acts in | d. Atmospheric pressure |
| 5. Withstands great pressure of water | e. Manometer |
| Column A | Column B |
| 1. A device used to measure pressure | e. Manometer |
| 2. Pressure due to the weight of the air above | d. Atmospheric pressure |
| 3. Unit of pressure | a. Pascal |
| 4. Atmospheric pressure acts in | c. All directions |
| 5. Withstands great pressure of water | b. Walls of a dam |
D – Answer the following questions
- What is Pressure in Physics? Give its SI unit.
Pressure is defined as the force applied per unit area on the surface of an object. It determines how concentrated a force is. The SI unit of pressure is the pascal (Pa), which is equal to one newton of force acting on one square meter of area (N/m²).
- Why are needles made pointed?
Needles are pointed to exert high pressure. Since pressure is force divided by area, a sharp tip has a very small surface area. This means even a small applied force creates enough pressure to pierce easily through materials like cloth or skin.
- Why does a balloon burst if too much air is blown into it?
A balloon bursts because the air inside exerts pressure on its rubber walls. When too much air is blown in, the internal pressure increases beyond the elastic limit of the rubber. The wall material can no longer stretch and withstand the force, causing it to tear and burst. - Define atmospheric pressure.
Atmospheric pressure is the force exerted per unit area by the weight of the air above us in the Earth’s atmosphere. It is caused by air molecules colliding with surfaces. At sea level, this pressure is approximately 101,325 pascals.
- How does the atmospheric pressure vary with altitude?
Atmospheric pressure decreases with an increase in altitude. This happens because as you go higher, the column of air above you becomes shorter and lighter, resulting in fewer air molecules and lower pressure. This is why it is harder to breathe on high mountains.
- Explain why the walls of the dam are made thicker at the base.
Dam walls are thicker at the base to withstand the increasing pressure of the water. Water pressure is directly proportional to depth; it is greatest at the bottom. A thicker, stronger base is needed to counter this immense force and prevent the dam from collapsing.