Revision – Chapters 5
1. What is the formula to calculate the apparent weight of a submerged body?
Apparent weight = True weight - Upthrust.
2. Does the loss in weight of a body depend on the shape of the body?
No.
3. Is the upthrust acting on a body the same at all depths, provided the body is fully submerged?
Yes.
4. What is the condition for a body to float on a liquid?
The density of the body ≤ density of the liquid.
5. Why does a balloon filled with helium rise in the air?
Because the upthrust due to air is greater than the weight of the balloon.
6. If a body's weight is equal to the upthrust, what is its apparent weight in the fluid?
Zero.
7. Why does a piece of iron sink in water but a large ship made of iron float?
The ship displaces a large volume of water, so the upthrust equals its weight.
8. What is the unit of relative density?
It has no unit (unitless).
9. Does Pascal's law apply to gases?
Yes.
10. What is the relationship between the force and area in a hydraulic machine?
F₁/A₁ = F₂/A₂ (constant ratio).
11. In a hydraulic press, what is the effect of applying a small force on a small piston?
It produces a large force on a large piston.
12. What is the principle behind a hydraulic brake system?
Pascal’s law.
13. What is the SI unit of thrust?
newton (N).
14. What is the main application of a hydraulic jack?
Lifting heavy loads.
15. How is a large force generated in a hydraulic machine?
By transmitting pressure from a small area to a large area.
16. What is the key advantage of using hydraulic machines?
Force multiplication.
17. What is the upward force exerted by a fluid on a body immersed in it?
Upthrust.
18. What is the SI unit of upthrust?
newton (N).
19. On what two factors does the upthrust on a body depend?
Density of the fluid and volume of submerged body.
20. What principle states that the upthrust on a body is equal to the weight of the fluid it displaces?
Archimedes’ Principle.
