Thrust, Pressure and Archimedes' Principle - UNSOLVED PRACTICE SET
Chapter: Gravitation | Topic: Thrust Pressure and Archimedes
THRUST, PRESSURE AND ARCHIMEDES' PRINCIPLE - UNSOLVED PRACTICE SET
Topic: Thrust Pressure and Archimedes
Multiple Choice Questions
Q1. Pressure is defined as:
- Force multiplied by area
- Force divided by area
- Mass divided by volume
- Weight divided by mass
Q2. A sharp knife cuts more easily than a blunt one because:
- A sharp knife has less area, so more pressure is exerted on the surface
- A sharp knife has more mass
- A blunt knife has less surface area
- Pressure is independent of area
Q3. Archimedes' Principle states that when an object is immersed in a fluid, it experiences an upward force (buoyant force) equal to:
- The weight of the object
- The weight of the fluid displaced by the object
- The weight of the entire fluid
- The mass of the object divided by the fluid's density
Q4. A ship made of steel floats on water even though steel is denser than water. This is because:
- Steel loses its density in water
- The shape of the ship causes it to displace water equal to its own weight, generating enough buoyancy
- Ships have magnets that push against the water
- Water density increases under the ship
Q5. The SI unit of pressure is:
- Newton (N)
- Newton per metre (N/m)
- Pascal (Pa) = Newton per metre squared (N/m²)
- Joule per kilogram (J/kg)
Q6. An object sinks in water if:
- Its density is equal to the density of water
- Its density is less than the density of water
- Its density is greater than the density of water
- It has rough edges
Short Answer Questions
Q7. Define 'thrust' and 'pressure'. How are they different from each other? Write the formula for pressure.
Q8. A soldier lying flat on snow walks on it safely, but if the same soldier stands upright, they sink into the snow. Explain this using the concept of pressure.
Q9. State Archimedes' Principle. A block of wood is placed in water and a metal ball of the same mass is placed in water. Which one floats and which one sinks? Why?
Q10. Why do objects appear to weigh less when submerged in water? Give a formula-based explanation involving buoyant force and apparent weight.
Q11. A submarine dives deep into the ocean and a hot air balloon rises in the sky. Explain how each uses Archimedes' Principle / buoyancy to operate.
Q12. Why are the foundations of tall buildings and dams made very wide at the base? Relate your answer to the concept of pressure.
Long Answer Questions
Q13. Explain Archimedes' Principle in detail. Include:
(i) the statement of the principle,
(ii) what buoyant force is and why it exists,
(iii) the conditions under which an object floats, sinks, or remains suspended, and
(iv) one real-life application each for floating, sinking, and suspension.
Q14. Describe how pressure varies with depth in a liquid. Explain:
(i) the formula for pressure at depth h (P = ρgh),
(ii) why water tanks are placed at height in Indian villages for water supply,
(iii) why the walls of a dam are thicker at the bottom, and
(iv) why deep-sea divers
Q15. An iron block sinks in water, but an iron ship floats. A balloon filled with helium rises in air, but one filled with CO₂ sinks. Using the concepts of density, buoyancy, and Archimedes' Principle, explain all four observations in a connected, detailed answer.
Numerical / Application-Based Problems
Q16. A rectangular block of dimensions 20 cm × 10 cm × 5 cm is placed on a flat surface. It weighs 10 N.
(i) What is the maximum pressure it can exert on the surface?
(ii) What is the minimum pressure it can exert?
(iii) On which face should it be placed to exert minimum pressure?
Q17. A metallic cube of side 10 cm is fully submerged in water.
(i) What is the volume of water displaced (in m³)?
(ii) What is the weight of displaced water?
(iii) Therefore, what is the buoyant force acting on the cube?
(Note: 1 cm³ = 10⁻⁶ m³)
Q18. A student finds that a stone weighs 2.5 N in air and 1.8 N when fully submerged in water.
(i) What is the buoyant force on the stone?
(ii) What is the volume of the stone? (Use ρ_water = 1000 kg/m³ and g = 9.8 m/s²)
(iii) If the stone were placed in a liquid denser than water, would the buoyant force increase or decrease? Justify.