i. The level of mercury is initially at the same level.
ii. The gas present in the manometer event pressure.
iii. The mercury level moves down in one limb and rises in other limb.
iv. The mercury level moves down in one limb and rises in other limb.
v. The difference in liquid pressure is measured.

Experiment:
i. Take a plastic bottle.
ii. Put three holes near the bottom at the same height.
iii. Fill the bottle with water.
Inference:
Water comes out from all holes with the same pressure at the same distance.
Reason:
Liquids exert the same pressure in all directions at a given depth.

1. Art upward force is exerted by water on a floating or a partially submerged body.
2. This is called buoyant force and the phenomenon is known as buoyancy.
3. Force is exerted not only by liquids but also by gases.
4. Liquids and gases together called as fluids.
5. Upward force decides whether an object will sink aor float.
6. If the weight of the body is less than upward force, then the object will float. If not, it will sink.
7. Buoyant force> Weight - floats
Weight> Buoyant force - sink.

Experiment:
i. Fix a sharp pin on a wooden board in rows and columns.
ii. A Big blown up balloon is placed gently over the pins.
iii. Place a small book on the top of the balloon.
Inference:
i. The balloon will not burst.
Reason:
i. A single pin produces a large pressure over a small area.
ii. Large number of pins exerts a very little pressure.
iii. The applied force gets distributed over a larger surface of the body.
So, the balloon will not burst.

Experiment:
i) Arrange some notebooks one over the other to form a platform on a table.
ii) Keep a wide scale, as a slide, such that one of its ends rests on the pile of books:
iii) Take different kinds of materials like cotton cloth, plastic paper, newspaper, writing pad etc.
iv) Place some glass marbles in a bowl placed on the table.
v) First, keep a rectangular piece of paper near the end of the scale which is in contact with the table.
vi) Now release a glass marble from the top end of the scale such that it rolls down the scale.
vii) Allow the marble to roll over the piece of paper and finally, come to rest.
viii) Measure the distance travelled by the marble over the paper using the meter scale.
ix) Replace the rolling surface by placing the plastic sheet, wooden plank, cotton cloth etc.
x) In each trial measure the distance travelled by the glass marble.
xi) Tabulate the distance covered by the marble over each surface.

Inference:
The marble covers a lesser distance over the cotton cloth in comparison with the distance it covers over the glass plate.
Reason:
i) A rough surface like the cotton cloth offers more frictional force. So the marble moves slowly and cover a minimum distance.
ii) The smooth surface of glass, offers lesser friction. So, the glass marble travels a greater distance over it.
Result:
i) The effect of the force of friction increases as the roughness of the surface increases.
ii) Thus friction depends on the nature of a surface.

Force is that which changes or tends to change:
(i) the state of rest
(ii) the state of uniform motion of a body.
(iii) the direction of a moving body.
(iv) the shape of a body

The amount of force or weight of the atmospheric air that acts downward on unit surface area of the surface of the earth.

i. At a higher altitude, due to the lack of atmospheric pressure, the boiling point reduces.
ii. So, the water boils even at 80^oC
iii. This thermal energy is not sufficient for cooking

i. Liquid pressure increases with depth.
ii. Pressure is high at the bottom of the sea.
So the deep sea divers wear special suits to protect themselves from high pressue, otherwise it crush' their bodies.

i. Liquids do not have definite shape.
ii. The force acting on unit area of the surface, on which the liquid is placed