1. What is buoyancy?

Ans: When a body is immersed completely or partially in a fluid, exerts an upward force on the body.
2.The weight of a body in air is 240N and weight in water is 190N. Find the buoyancy of water?

Ans: weight of body in air= 240N

weight in water=190N

Buoyancy=wt in air- wt in water

=240-190

=50N
3.The weight of the body in air is 150N. It experiences 30N buoyancy from water. Find out the weight of the body in water?

Ans: Weight in air = 150 N

Buoyancy = 30 N

Weight of the body in water = 150-30

=120N
4.What are the factors that influence buoyancy?

Ans: Density of the liquid

Volume of the object
5.State

a. Archimedes principle

b. principle of floatation

Ans: a) When an object is immersed partially or completely in a fluid the buoyancy experienced by it will be equal to the weight of the fluid displaced by it.

b)weight of a floating body is equal to the weight of the fluid displaced by it. or

weight of the 0bject =buoyancy=weight of the fluid displaced

Note: When a body is fully immersed in a fluid the volume of the displaced fluid will be equal to the volume of the body.
6.State pascal’s Law

Ans: The pressure applied at any point of a liquid at rest in a closed system will be experienced equally at all parts of the liquid .
7.What is the basis of pascal’s law?

Ans: Volume of a liquid cannot be changed using pressure.

8.Name some devices that work on the principle of Pascal’s law.

Ans: Hydraulic jack, Hydraulic lift, Hydraulic press, Excavator, Hydraulic brake
9.a. What is surface tension?

b. Which attractive force between molecules is responsible for surface tension?

Ans: a) Due to the mutual force of attraction of molecules on the surface of water, the surface acts like a stretched membrane

b)cohesive force
10.The area of one end of a U tube is 0.01m² and that of the other end is 1m². When a force was applied on the liquid at the first end, the force experienced at the other end was 20,000N. What was the force that applied on the liquid at the first end?

Ans: A 2 = 1 m 2

F 2 = 20000 N

F 1 / A 1 = F 2 /A 2

F 1 = (F 2 x A 1 ) /A 2

= 20000×0.01/ 1

=200N
11.What is viscosity?

Ans: Viscosity is a characteristic property of a liquid to oppose the relative motion between its different layers.
12. How temperature affects viscosity?

Ans: When temperature increases the viscosity of a liquid decreases.
13. What is adhesive force?

Ans. Force of attraction between molecules of different types of substance.
14. Write the equation to calculate relative density? Which is the instrument used to measure relative density?

Ans: a) Density of substance Density of water

b) Hydrometer
15.What are the reasons for the following situations.

a. A stone experience loss of weight while inside water.

b. Ink can be blotted with chalk.

c. Though an egg sinks in pure water, it will float on salt water

Ans: a) Buoyancy

b) Capillarity

c) Density of pure water is less than that of salt water.
16. When does capillary depression occur?

Ans: When the cohesive force is greater than the adhesive force.
17. Define mobile liquids? Give examples.

Ans: Liquids of lower viscosity. eg: kerosene spirit,
18.Define viscous liquids? Give examples

Ans: Liquids of greater viscosity

eg: Honey, Glycerine