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Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Why Bodies float ?

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Page 1: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat 13.Why bodies float

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 2: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

13.1.Thrust13.2. Pressure in Fluids 13.3. Pressure Exerted by a gas13.4. Liquid Pressure13.5. Buoyant Force13.6. Archimedes’ Principle13.7. Relative Density

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 3: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

THRUST13 .1.Activity

1)Press your thumb against a piece of paper•Now press the pointed end of a pin against the same piece of paper.•Do you notice any difference?•Answer- When pressed , the pointed end of the pin presses easily through the piece of paper. That does not happen when we press the thumb against the piece of paper.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 4: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

• The force acting on an object perpendicular to the surface is called thrust.

• The thrust on a unit surface area is called pressure. Pressure= thrust/areaSI unit of pressure is N/m2 . It is also called pascal in

honour of the scientist Blaise Pascle

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 5: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

BLAISE PASCAL• He was a French physicist and mathematician. He formulated pascal's law of pressure.He

constructed mercury Barometer and measuring air pressure.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 6: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

PRESSURE IN FLUIDS

• Activity Take two rubber balloon. Fill one with water and blow air into other. Now prick both balloons with a pin. What do you observe? Answer-Water and air both come out of the balloons. Air escapes

quickly compared to water and produces a loud sound.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 7: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

FLUIDS• Liquids and gases are called fluids.• Fluids exert pressure on the base and walls of

the container that holds them, due to weight of fluid.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 8: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

PRESSURE EXERTED BY GAS• Activity Take an empty can Pour small quantity of water in it . Boil this water for a few minutes until

the steam has driven out the air. Now close the can with the stopper tightly. Allow it to cool by pouring cold water over it. What do you observe? Answer- The can gets gradually crushed.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 9: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

• In the atmosphere , the force exerted on the unit surface area by the weight of the air column above it is called the atmospheric pressure.

• At the sea level it is about 105 N/m2

Page 10: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

THINK WHY?• Some people feel their ears popping at the top

of a mountain.• Some people feel breathless as they climb

higher and higher on a mountain.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 11: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

LIQUID PRESSURE• Pressure increases with the depth and is

proportional to the density of the liquid.• P d h

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 12: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Buoyant force

1] Take a full bucket of waterTry to push inverted glass bottle into bucket.

What do you experienced?Answer-we experienced that an upward force

on the bottle due to the water in the bucket opposing the downward motion of the bottle.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 13: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

• The upward force exerted by a liquid(a fluid an general)on a body completely or partially immersed in it is called upthrust or buoyant.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 14: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

ARCHIMEDES C. 213 7 – 212 BC Greek mathematician, physicist

and engineer First to calculate the ratio of a

circle’s circumference to it’s diameter (π)

Calculated volumes of various shapes

Discovered the nature of the buoyant force

Inventor of many practical devices: Catapults, levers, screws, etc.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 15: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

ARCHIMEDES’ PRINCIPLE

When a body is immersed partially in a fluid , it experiences an upward force that is equal to the weight of the fluid displaced by it

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 16: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

DENSITY & RELATIVE DENSITY• Ratio of mass to volume is called density.• Density = mass / volume• SI unit is kg/m3 and CGS UNIT is g/cm3.

• Relative density = density of substance / density of water.

• It is also called specific gravity of a substance. It has no unit.

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 17: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

EXAMPLECalculate pressure exerted by a screw on the wooden

plank if area of contact of the screw is 0.5 mm2 and its weight is 50 N.

Given : Area = 0.5 mm2 0.5 X 10-6 m2

weight of the screw = thrust = 50 Npressure = ?

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 18: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

10-6

Solution : pressure = thrust area = 50 0.5 x 10-6 10-6

= 100 x 10-6 N/m2

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

Page 19: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

2) A metal block having mass 10 kg with its length 50 cm, breadth 20 cm and heigth 10 cm. Calculate pressure exerted by metal block when it is mead to lie on a table top with surface – (a) ABCD (b) DCFE (c) BCFG. Solution : Thurst = Weight of metal block = mg = 10 X 9.8 = 98 N

Page 20: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

(a) For surface ABCD, L = 50 cm, b = 20 cm Area = length X breadth = 50 cm X 20 cm = 1000 cm2

= 0.1 m2

Pressure = Thrust Area = 98 0.1 = 980 N/m2

Page 21: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

(b) For surface DCFE , l = 50 b = 10cm Area = length x breadth = 50 cm x 10 cm

= 500 cm2

= 0.05m2

pressure =

= 98

= 1960 N/m2

Thrust Area

0.05

Page 22: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?

(c) For surface BCFG, l = 20 cm b = 10cm Area = length x breadth = 20cm x 10cm = 200 cm2 = 0.02 m2 Pressure =

= 98

= 4900 N/m2

Thrust Area

0.02

Page 23: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

EXAMPLE• If density of water is 103 kg/m3 and density of copper is 8 .9 X

103 kg/m3 . Calculate relative density of copp?Given-Density of water-103kg/m3

density of copper-8.9X103kg/ m3 Relative density = Density of copper

Density of water = 8.9X103 kg/m3

103 kg/m3

= 8.9

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float

Page 24: Logylogyat 13.Why bodies float Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara. Std-9 th Sub-Science &Technology Topic- Logylogyat

Logylogyat

Rayat Shikshan Sanstha,Karmaveer Vidyaprabodhini,Madhya vibhag,Satara.

Std-9th Sub-Science &Technology

Topic-

Logylogyat

Why Bodies float ?