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1. NAME: ABHINAV KUMAR AND ISHAAN
AGGARWAL
ROLL NO.=40 AND16

2. THRUST
 “The force acting on an object perpendicular
to the surface is called THRUST”.
 In other words “It is the force acting
perpendicularly on a surface”.
 SI unit is N or Newton.

3. PRESSURE
 “The effect of thrust per unit area” is called
Pressure.
 Pressure =thrust/area
 SI unit is Pa or Pascal.
 Pa =N/m².

4. Pressure depends upon 2
factors :
 Force(thrust)-more force more pressure.
 Area- more area less pressure.
“The same force produces less pressure if it acts on a
large area but can produce less pressure if act on a small
area”.

5. EVERYDAY OBSERVATION
 1. A simple example of pressure may be seen
by holding a knife to a piece of fruit. If you hold the
flat part of the knife against the fruit, it won't cut the
surface. The force is spread out of a large area (low
pressure).

6.  2. When we are standing, both are feet are in
contact with the ground while when we are
walking, one of our feet is always in air. Hence, the
area in contact with the ground is more when we are
standing than when we are walking. Greater the area in
contact, lesser would be the pressure.

7. PRESSURE IN FLUIDS
FLUIDS: Any substance which can flow due to its
internal forces is called FLUIDS.
 Gases and Liquids are considered as fluids whereas
solids are rigid.

8. BUOYANT FORCE : FLOATING
PRINCIPLE (BUOYANCY)
 BOUYANCY: “It is the principle by which the fluid
exerts a force in upward direction on the solid object
immersed into the fluid ”. This upward force is called
Buoyant Force which is also known as UPTHRUST.

9. EXAMPLE

10. ARCHIMEDES `PRINCIPLE
 “When an object is wholly (or partially) immersed in a
liquid, it experiences a buoyant force (or upthrust)
which is equal to the weight of liquid displaced by the
object”.
 In other words
Buoyant force (or upthrust)=Weight of the liquid
acting on an object displaced by that object

11. APPLICATIONS OF ARCHIMEDES
`PRINCIPLE
 1.Archimedes` principle is used in determining the
relative density of an substance .
 2.The hydrometers used for determining the density of
liquids are based on Archimedes` principle.
 3.The lactometers used for determining the purity of
milk are based on Archimedes`principle.
 4.Archimedes`principle is used in designing ships and
submarines.