Remember it's just a start for class 20 students. Just a way to declare hot to teach students of class by using the scope of ICT . It declares the scope of ICT in the field of education.
1. Albert Einstein
Born in 14 March 1879 and died in 18 April 1955
Best known for his mass-energy relation equivalence
formula. i.e E=mc2 and theory of relativity.
Received the Nobel Prize in 1928 for his discovery of
the law of the “photoelectric effect” in physics.
4. What is gravity and gravitational force?🤔🤔
• The unseen force of the earth that pulls the object towards the center of its
surface is called gravity.
• The mutual force of attraction between two bodies is termed as gravitational
force.
• Sometimes curiosity arise why this water always go downwards than upwards
. You have also got some ??? So why everything goes downwards the earth
surface ,The only answer is Gravity of the earth.
5. Different theories regarding center of the
universe
• Until sixteenth century, the earth was considered as the center of the
universe and all the other heavenly bodies revolve around it. This theory is
termed as Geocentric theory.
• But later on, Nicholas Copernicus, an astronomer claimed that the sun is the
center of the solar system and all the planets revolve around it. This theory
was termed as the Heliocentric theory. Then he was accused of revolting
Christianity and he was burnt alive.
• Later, Galileo claimed this theory.
6. Who founded the gravity then?🤔🤔
• Newton focused hid research on finding the reason of the motion of the
planets around the sun. he found a solution and established his famous
Universal Law of Gravitation.
• According to him there was force of attraction between the bodies called
gravitational force.
• As the bigger wins there is a strong gravitational force of the sun so all the
planets revolve around the sun.
• Combined masses of all planets and satellites=o.oo15 part of the sun.
7. Newton’s Universal Law of Gravitation
• It states that “The mutual force of attraction of the two bodies is directly
proportional to the product of their masses and inversely proportional to the
square of distance between their centers.”
8. Prove that :F=Gm1m2/R2
If two masses of 1kg each are kept at 1m apart then the gravitational
force is equal to gravitational constant(‘G’).
Therefore, the universal gravitational constant is defined as the
gravitational force between two bodies of unit masses that are kept at a
distance of 1m from their centres.
Value of G is numerically equal to 6.023*1023 Nm2kg-2 which is measured
by Henry Cavendish in 1810 AD by using a sensitive balance/
9. Factors affecting gravitational force:
• Product of the masses of the bodies
Fαm1m2
• Distance between the centers of the bodies.
F α 1/d2
10. Exercise:
Find the change in gravitational force when
1. Masses of both the objects are doubles keeping the distance constant.
2. Both the masses of the bodies are halved but distance is kept constant.
3. Distance is halved by keeping the masses constant.
4. Distance is doubled by keeping mass constant.
5. Masses are doubled each and distance is halved.
6. When distance is decreased by four times keeping masses constant.
11. Characteristics of the Universal Gravitational
Constant:
• Independent of the medium in which the objects are kept.
• Independent of the masses of the objects.
• Independent of the physical factors such as state of object, temperature,
pressure, chemical composition and distance between objects.
• Therefore, it is called universal gravitational constant.
12. Gravity and effect of gravity:
• Gravity is the force of attraction experienced by an object kept inside the
gravitational field of a heavenly body.
• It holds the atmosphere around the earth.
• It develops acceleration to the falling bodies.
• It helps water to flow.
• Every object falls towards the surface from a certain height.
• Existence of solar system and heavenly bodies.
• Causes of revolution of planets around the stars.
13. Gravity of an object on the surface of the
earth:
• Like the earth has got a gravitational force other planet has also got a gravity
in it.
• The moon also has a gravity as that of earth. Thus, it has been proved that
the gravity of the moon is 1/6 of that of the earth.
• Therefore, a person who can jump 1m on the earth can jump 6m on the
moon surface.
• Similarly, if a person can lift a load of 60kg(600 N) on the earth then he/she
can lift 360kg (600N) on the moon’s surface.
14. Gravity depends on following factors:
• Mass of the heavenly body:
FαM(foe constant mass of the object and radius of the heavenly
body)
• Mass of the object on the heavenly body:
Fαm(for constant mass and radius of the earth)
• Radius of the heavenly body:
Fα1/R2(For constant mass of heavenly body and object.)
15. Measure of the gravity at a certain height :
• W=GMm/(R+h)2
•Derive it for student.
17. Acceleration due to gravity:
• Acceleration produced on a freely falling body because of the gravitational
force or gravity is called acceleration due to gravity.
• Acceleration due to gravity on the surface of earth is denoted by “g” and is
expressed in meter per second square(m/s2). The value of g on earth is 9.8
m/s2 but on the moon’s surface is 1.62 m/s2 .
• The acceleration due to gravity at a certain place is always constant.
18. What do you mean by acceleration due tp
gravity of earth surface is 9.8 m/s2?
• The acceleration due to gravity at a certain place is ……..
Means it changes its speed by ……m/s in every 1
second..
20. Derivation of acceleration due to gravity at
different places or at different height:
• Do it yourself to make understand to the student.
21. Differences between ‘g’ and ‘G’
G(universal gravitational
constant)
• It is the force of attraction between
two bodies of unit masses each
separated by unit distance between
their centers.
• It is universally constant.
• It is a scalar quantity.
• Its unit is Nm2/kg2.
g(acceleration due to gravity)
• It is an acceleration produced on a
freely falling bodies under the force of
gravity.
• It varies from one place to another
place or from one heavenly body to
another.
• It is a vector quantity.
• Its unit is m/s2.
22. Differences between mass and weight:
Mass
• It is the measure of the quantity of the
matter present in a body.
• It is a scalar quantity.
• It is a constant for a classical body.
• It is measured using a beam balance.
• Its SI unit is kg.
Weight
• It is the measure of force of attraction
of a heavenly body on a body.
• It is a vector quantity.
• It varies from one place to another.
• It is measured with a spring balance.
• Its SI unit is N.
23. Freefall and weightlessness:
• When a body falls only under the
influence of gravity without any
external resistance, the motion of
the body is said to be a freefall.
• Weightlessness is defined as the
state in which the apparent weight
of the object is zero.
24. 1.Weightlessness caused by freefall:
• Since the apparent weight of object is
R=m(g-a)
But for a freely falling body a=g,
R=m(g-g)
R=m*0
R=0
i.E the object is in the condition of weightlessness.
25. 2.Weightlessness on spacecraft revolving on a
circular orbit:
• An astronaut in a spacecraft revolving around a heavenly body feels
weightlessness because of the freefall.
• Remember that bigger masses can create its own gravitational field but the
spacecraft isn't so massive to create its own gravitational field.
• The body inside the satellite is in state of freefall therefore the body appears
to have no weight as the spacecraft moves in the gravity of the earth rather
than producing its own acceleration to move forward in a linear motion.
26. 3.Weightlessness at null zone:
• There is a zone in the outer space where there is no effect of gravity i.e. g=0.
• Such points are called null points.
• The weight at the null point is given by:
W=mg
W=m*0
W=0
and the state is called true weightlessness. (Real weghtlessness)
27. Motion of a parachute jumper(Paratrooper)
• When a paratrooper jumps from a certain height, at first s/he falls with
acceleration due to gravity but after opening the parachute the velocity
changes as it is affected by air resistance.
• When the air resistance and weight of the paratrooper becomes equal then
the acceleration of the paratrooper becomes zero and the paratrooper with a
parachute falls with a uniform velocity. This uniform motion helps him/her
to land safely on the ground.
28. 4.Weightlessness at center of the earth:
• Body at the center of the earth has zero weight.(as at center g=0)
It is a apparent weightlessness.
29. Motion of a parachute jumper(Paratrooper)
• When a paratrooper jumps from a certain height, at first s/he falls with
acceleration due to gravity but after opening the parachute the velocity
changes as it is affected by air resistance.
• When the air resistance and weight of the paratrooper becomes equal then
the acceleration of the paratrooper becomes zero and the paratrooper with a
parachute falls with a uniform velocity. This uniform motion helps him/her
to land safely on the ground.
30. Questions from me:
1. What is the force between two bodies of mass ‘A’ and ‘B’ that lie at a
distance ‘C’ ?
2. Why does the value of ‘g’ differ from place to place?
3. Why does stone and a piece of paper dropped together from a height not
reach the earth’s surface together?
4. It is a difficult to lift a heavier stone than a lighter one. Why?
5. Why does the weight of an object greater at poles than at the equator?
31.
32. Pressure??🤔🤔
• Pressure is defined as the force acting per unit area perpendicular to the
surface.
• When a force (F) acting on a surface area (A) in contact the pressure exerted
is given by:
• Pressure=Force/Area
• Pressured is measured in N/m2 or Pascal.
33. Application of pressure:
1. A sharp knife cuts easily than a blunt one because of the smaller area of
the knife, it exerts the higher pressure.
2. Railway tracks are laid on a large sized wood sleepers . It helps in increase
in area, reduces effective pressure.
3. Studs are made on the sole’s of football player. It helps to increase the
pressure on ground and hence players can paly without skidding.
34. What is liquid pressure?🤔🤔
• The pressure exerted by liquid on the wall of the vessel is called liquid
pressure.
• Liquid pressure depends upon:
1. depth of the liquid(h)
2. density of the liquid(d)
3. acceleration due to gravity of the place(g)
35. • The properties of the liquid pressure:
1. Liquid pressure at a point doesn't depend on the volume of the vessel but
on the depth of the liquid.
2. Pressure applied on the liquid is transmitted equally in all directions.
36. Pascal’s Law and how to verify::🤔🤔
• Pascal’s law states that “Liquid pressure transmits to all direction equally.”
Verification using a circular chamber having four holes and applying a pressure
from one side which is transmitted to all three others equally.
37. Applications of Pascal law:
Hydraulic Press
• Hydraulic press is based on Pascal’s law.
• It uses hydraulic cylinders to produce compressive force.
• It is device that is used for compression and as a lifting device in sea ports
and industries.
• Principle:
1. liquid is almost incompressible.
2. Liquid transmits equal pressure in all directions.
38. Working
Derive the formula by yourself:
(F1/A1)=(F2/A2)
i.E the force is multiplies by A2/A1. Greater the ratio of A2 and A1 greater is
the multiplication of the applied force.
39. Application area of Pascal’s law/Hydraulic
machine
• Hydraulic press
• Hydraulic garage lift
• Hydraulic brakes
• Cranes
40. Density of the liquid:
• The total mass per unit volume of a body is called density of that body.
• It is measured in kg/m3.
• Density=Mass/Volume
• The density of water at 4°C is 1000 kg/m3 i.e 1g/cm3.
• Any object having density more than that of water sinks into water and the
object with density less than that of water floats in it.
41. Relative Density(R.D.)
• The ratio of density of a substance to the density of pure water at 4°C is called
relative density. R.D=
𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑡ℎ𝑒 𝑜𝑏𝑗𝑒𝑐𝑡
𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 4°C
• It can also be defined as the ratio of mass of substance to the mass of the same
volume of water at 4°C . R.D=
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑎 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑎𝑚𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 4°C
• Relative density has no unit as it is a ration.
• If we add impurities in water then the density of the water gets increases.
• Example: density of salt solution is greater than water.
42. Up thrust :
• When a body is immersed partially or completely in a liquid the net upward
thrust exerted to the body by the liquid is called up thrust.
• It reduces the weight inside the liquid of a body.
• Up thrust doesn’t depend upon the mass of the body but depends upon the
volume of liquid displaced in the vessel by the body.
• It is explained by Archimedes principle.
43. Reason of up thrust:
• When a body is put in a medium, it occupies some volume in that medium.
We know that the medium was earlier occupying the whole available space,
so some of the particles of medium must have been pushed by the body.
• And according to Newton's third law of motion, for every action there's
equal and opposite reaction. So the particles of medium push back the body,
resulting in up thrust.
44. Factors on which up thrust depend:
• The volume of submerged part of a body:
Upthrust α Volume of submerged part of solid.
• Density of liquid:
Upthrust α Density of the liquid
45. Archimedes principle:
• Archimedes' principle states that “When a body is immersed completely or
partially in a fluid, it experiences an upward force that is equal to the weight
of the fluid displaced by the body.”
• He is a Greek scientist.
• He was a great mathematician, physicist, and astronomer of his time.
47. Law of floatation and verification::
• Law of floatation is a special condition of Archimedes' Principle which
states that the weight of a floating body is equal to the weight of the
displaced liquid.
•Verification from book
48. Application of principle of floatation:
In transportation by water ways
The law of floatation is applied in all vessels which travel by waterways that
include ships, submarines and ferry boats.
In transportation by air ways
It is also applied in some vessels which travel by air ways such as hot air balloon and air ship.
In decoration
Balloons of different colors and shapes are filled with lighter gas so that will float in air.
In measurement of specific gravity of liquids
Hydrometer is an instrument which is used to measure specific gravity of liquids, in its operation
it employs the law of floatation.
Other uses include making of bulges and transportation of logs down the river.
49. CONDITIONS FOR OBJECTS TO
FLOAT
I. The average density of the object should be less than the density of the fluid in which
the object has to float.
Example, a ship is very heavy but it floats because it is hollow inside it contains
air, this causes its average density to be lower than that of water.
II. The Upthrust force of the fluid on the object must be equal total
weight of the object.(law of floatation)
Example, a coin will sink to the bottom when placed on the surface of water, this
is because the upthrust of water on coin is less than its weight
III. The volume of object submerged must be large so as to displace large amount of fluid.
50. Mercury barometer
Mercury Barometer is the simplest device to
measure atmospheric pressure at a location. It
consists of a glass tube closed at one end
immersed in a container filled with mercury.
Because of the atmospheric
pressure mercury rises in the tube
51. Applications of atmospheric pressure:
• Use of straw pipe in drinking
• Filling inks in a pen
• Use of syringe in medical field
• Use of air pumps in filling up air
• Use of lift pump
52. Some instruments based on atmospheric
pressure:
1. Syringe:
A medical device that is used to inject
fluid into, or withdraw fluid from, the body. A
medical syringe consists of a needle attached to a
hollow cylinder that is fitted with a sliding plunger.
When the piston is pulled the needle draws
medicine liquid and the medicine enters the
cylinder following the effect of atmospheric
pressure.
53. Downstroke and Upstroke:
• Pushing piston down
is called downstroke.
• Pulling piston up is
called upstroke.
54. Questions from me:
1. Define Torricelli.
2. What length of vacuum tube is taken for mercury barometer?
3. How many valves are there in water pump? Where do they lie?
4. How does a hydraulic press function?
5. What happens during downstroke and upstroke of a water pump?
6. How can we fill up liquid into a syringe?
7. How much weight is over your head(say 0.0125 m2)?
55. Antoine Lavoiser
• Born on 20 August 1743.
• Died n 8 May 1794.
• French chemist.
• Father of chemistry.
• Recognized and named oxygen and hydrogen
and is best known for combustion and
stoichiometry.
58. Atoms, Molecules, Elements and Compounds.
• The smallest particle of a chemical element that can exist is called atoms.
• A group of atoms bonded together, representing the smallest fundamental
unit of a chemical compound that can take part in a chemical reaction are
called molecules.
• A substance that cannot be broken down into simpler substances by
chemical means is called Atoms.
• A thing that is composed of two or more separate elements; a mixture is
called compound.
59. Mendeleev’s periodic table:
• Dmitri Ivanovich Mendeleev’s propounded this in 1859
• Mendeleev realized that the physical and chemical properties of elements
were related to their atomic mass in a 'periodic' way, and arranged them so
that groups of elements with similar properties fell into vertical columns in
his table.
• He stated his periodic table as “The physical and chemical properties of
elements are the periodic functions of their atomic weights.”
60.
61. Groups and Periods:
• The vertical columns are called groups.
• The horizontal rows are called periods.
62. Features of Mendeleev’s Periodic table:
• i) Elements arranged in increased atomic mass. Elements, with
similar properties grouped together in periods (horizontal rows)
and columns (vertical rows).
ii) There are seven periods and eight columns.
iii) Each column of first seven are subdivided into A and B
subgroups. Eighth column contains three elements each in 4, 5
and 6 periods.
63. Drawbacks of Mendeleev’s Periodic table:
• 1) Position of hydrogen= hydrogen resembles both with halogens as well as alkali
metals. it forms the positive ions like metals and negative ions like halogens. so
position of hydrogen was not justified.
• 2) Position of isotopes= position of isotopes could not be explained there was no
space for isotopes although they different atomic masses.
• 3) Wrong order of atomic masses of some elements as mentally has place the
elements in increasing order of atomic masses but Cobalt is placed before nickel to
measure chemical property of the group this anomaly was not explained by
Mendeleev.
64. • 4) Similar elements in different groups and some elements with similar
properties have been placed in different groups were placed.
• 5) Cause of periodicity is not explained it was not explained that why the
elements of same group show resemblance in their properties.
65. Advantages of Mendeleev’s Periodic table:
• 1. Grouping of elements. He generalized the study of the
elements then known to a study of mere 8 groups.
• 2. Gaps for undiscovered elements. Mendeleev left some gaps in
his periodic table. These gaps were left for subsequent inclusion
of elements not known at that time. He correctly thought that
such elements would be discovered later.
66. • .3. Prediction of properties of undiscovered elements. He predicted the
properties of then unknown elements om the basis of properties of
elements lying adjacent to the vacant slots.
• 4. Incorrect masses corrected. He was able to correct the values of atomic
mass of elements like gold and platinum by placing these elements strictly on
the bases of similarities in their properties.
