PHYSICS CLASS 9 th WRITTEN BY: SIR GHALIB ABBAS Ph: 03346718817 100% PASSE...
WRITTEN BY: SIR GHALIB ABBAS
Ph: 03346718817 100% PASSED
COMPOSED BY: MUHAMMAD RASHID UL HASSAN SAEEDI
Q.1 What is Science?
Ans . Science :
The knowledge gained through observation experimentations is called science.
Q.2 What is Physics? Write the name of its branches.
Ans . Physics:
It is that branch of science which deals with the study of the properties of matter ,energy and their mutual relationship .
Branches of Physics :
1)Mechanics 2)Heat 3)Sound 4) Light 5) Atomic physics 6)Nuclear physics 7) Plasma physics 8) Geo physics 9) Electricity and Magnetism .
Q.3 What is Plasma?
Ans. Plasma:
Matter assumes the state of gas ,comprising of ions and electrons at very high temperature .
Q.4 What is Plasma Physics and Nuclear Physics?
Plasma Physics:
The study of the properties of matter in this state is called Plasma Physics.
Nuclear Physics:
It deals with the properties and behavior of nuclei and the particles with in the nuclei.
Q.5 What are Physical Quantities? Give two examples.
Physical Quantities:
All measurable quantities are called Physical quantities. e.g Length Mass Time and Temperature.
Q.6 What are basic quantities? Write the name of the basic quantities.
Ans . Basic Quantities:
The unit of a base quantity is called a base unit.these are the 7 basic quantities;
1)Length 2)Mass 3)Time 4)Mole 5)Temperature 6)Electric Current 7)Intensity of light
Q.7 What are Derived units? Write some examples.
Ans. Derived Units:
Those units which are derived from basic units are called Derived Units. e.g speed ,velocity,energy
Q.8 Identify the base quantity in the following. 1)Speed 2)Area 3)Distance 4)Force
Ans Distance is a base quantity.
Q.9 Identify the following as base or Derived quantity . Density, force , mass, speed ,time,
length, volume , temperature
Ans. Base Quantities Mass , time , length , temperature
Derived Quantities Density , force , speed , volume
Q.10 Define Scientific Notation. Give one example.
Ans. Scientific Notation:
The method in which digits are written in some power of ten is called scientific notation.
e . g the scientific notation of 340000 is 3.4x105 .
Q.11 Write the numbers given below in scientific notation.
(a) 3000000000ms-1(b)6400000m (c)0.0000000016g (d)0.0000548s
Ans = 3x109ms-1(b)=64x105m=6.4x106m (c)16x10-10g=1.6x10-9g(d)548x10-7s=5.48x10-5s
Q.12 What are measuring instrument? Writes the name of measuring instrument
Which are used in Physics.
Ans Measuring Instrument:Those which are used to measure various physical quantities.
1)Metre Rule 2)Measuring Tape 3)Screw Gauge 4)Vernier Calipers
Q.13 What are Vernier Calipers and Screw Gauge . For what purpose they are used?
Ans Vernier Callipers:
It is that instrument which is used to measure the correct length of 0.1mm.The least count of vernier calipers is 1.01mm.
Screw Gauge:
It is that instrument whech is used to measure length up to 0.01mm.The least count of Screw Gauge is 0.01mm.
Q.14 Write the two names of Mass Measuring Instruments.
Ans 1) Physical Balance 2)Lever Balance 3)Electronic Balance
Q.15 What are Significant Figures? Give Examples.
Ans Significant Figures:
The accurately known digits and first doubtful digit in any measurement is called Significant Figures.
e.g in 5.731cm3 volume of a cylinder has the significant figure three .
Q.16 Define Rest and give example.
Ans Rest: If a body does not changes its position with respect to some observer then
it is said to be a state of Rest .e.g a book is lying on the table.
Q.17 Define Motion and give example.
Ans Motion: If a body changes its positions with respect to some observer then it is
said to be a state of Motion .
Q.18 How many types of Motion ?Write the names.
Ans Names: There are three types of motion.
1) Translatory Motion 2)Rotatory Motion 3)Vibratory Motion
Q.19 Define Translatory Motion. Give one example.
Ans It is that type of motion in which every particles of body has exactly the same motion is called
Translatory motion .e.g. motion of a gas molecule.
Q.20 How many types of translatory motion? Write its Names.
Ans: There are three types of translatory motion.
1)Linear Motion 2)Circular Motion 3)Random Motion .
Q.21 Difference b/w Linear and circular motion ?Give an example.
Ans: Linear Motion:
It is that motion in which body moves in a straight line .e.g. motion of a freely falling bodies.
Circular motion:
It is that motion in which body moves in a circular path .e.g . motion of the sum around the earth.
Q.22 Define Random motion .
Ans. Random Motion:
It is that motion in which a body movies in an irregular manner. e.g motion of gas molecules .
Q.23 Difference b/w Rotatory and Vibratory Motion ?Give an example.
Ans. Rotatory Motion:
It is that in which a body moves around a fixed point of axis .e.g .motion of ceiling electric fan.
Vibratory Motion:
It is that in which a body moves to and fro about a point and repeats its motion again and again about the same point. e.g Motion of swing .
Q.24 What are vector and scalars? Write five example of each.
Ans. Vectors:
Those quantities which have magnitude and direction are called Vector .e.g. force, weight,
acceleration torque ,momentum etc.
Scalars:
Those quantities which have only magnitude but no direction are called Scalar. e.g. Speed,
Time, Volume , Energy ,Work etc.
Q.25 What is position?
Ans. Position:
The distance in the direction of a body from a fixed point shows its position.
Q.26 What is difference b/w distance and displacement?
Ans. Distance:
When a person goes to Islamabad from Lahore through motorway .When he checks the meter,
realize that he has covered by a distance of 400 km. It is the total distance covered by the person.
Distance is a scalar quantity.
Displacement:
The shortest distance between two points is known as displacement. Displacement is a vector
quantity.
Q.27 What is difference b/w Speed and Velocity ?
Ans: Speed
Distance covered by a body in unit time is called Speed of body . e.g When a body covers 5m
distance in 1 second then the speed of body will be 5m/s.
If a body covers distance ‘S’ in time ‘t’ then its speed ‘V’ can written as:
Speed= distance/time
V=S/t
The unit of a speed is meter per second (ms-1) or kilometer per hour (km-1)
Velocity:
Distance covered by a body in unit time in particular direction is called Velocity of that body in
that direction. e.g. when a body covers 5m in 1 seconds along east , then the velocity of the body
5m/s in east .Velocity is a vector quantity. The unit of velocity is meter per second (ms-1) or
kilometer per hour (kmh-1)
Q.28 What is difference b/w uniform speed and uniform velocity?
Ans: Uniform speed:
A body has uniform speed if it covers equal distance in equal intervals of time however may be.
Uniform velocity :
A body has uniform velocity if it covers equal displacement in equal intervals of time however
short the intervals may be.
Q.29 How can cheetah run with a speed ?
Ans. Cheetah can run at a speed of 70 kmh-1.
Q.30 What is LIDAR gun?
Ans: (1) A LIDAR gun is used as light detection.
(2)It is use to calculate the vehicle’s speed .
Q.31 What is acceleration ?Write its units.
Ans: Accelration :
The rate of change of the velocity of a body is called acceleration.
The unit of the acceleration is meter per second square (ms-2).It is denoted by ‘a’.
Q.32 Write the equation of Motion.
Ans: Equation of Motion:
There are three equations of motion.
(i) Vf = vi+at
( ii ) S =Vit +1/2 at2
(ii) 2as =vf2 –vi2
Q.33 What is Gravitational acceleration ?Write its value .
Ans : That acceleration which is produced due to earth is called gravitional acceleration.It is denoted
by ‘g ‘.The value of ‘g’ is10m-2.
Q.34 Difference b/w Kinematics and Dynamics?
Ans: Kinematics:
It is the study of motion of bodies with out any reference to mass or force is called kinematics.
Dynamics :
It is the study of motion of body under the action of force.
Q.35 What is force ?Write its unit .
Ans Force:
Force is the angency which changes or tends to change the state of rest or uniform motion of a
body
Unit of force:
In S.I the unit of fore is unit Newton.
Q.36 What is Inertia ?
Ans: Inertia :
It is that property of a body due to which it resists against any change in its state of rest or of
uniform motion.
Q.37 What is momentum ?Write its unit.
Ans: Momentum
The product of mass and velocity is called momentum.If momentum is denoted by ‘P’ ,mass
denoted by “m” and velocity denoted by “v” then we can write P = mv
In S.I unit of the momentum is Kilogram meter per second (kgms-1).
It can also be written as Newton Second (N.S).
Q.38 State the First Law Of Motion.
Ans First Law of Motion:
This law states that everybody continues in its state of rest or if uniform motion in a straight line unless it is complete to change that state by an external source impressed upon it.
Q.39 State the second law of motion . Write its formula.
Ans. Second Law of Motion :
This law states that when a force acts upon a body an acceleration is produced in the direction of
a force and the magnitude of the acceleration is directly proportional to the force and is inversely
proportional to the mass of the body .The formula of motion is given as F = ma
Where F = Force , m = mass and a=acceleration
Q.40 State the Third Law of Motion. Give one example.
Ans Third Law of Motion:
This law states that action and reaction are equal in magnitude but opposite in direction .
e.g Motion of a man on earth is a good example of third law of motion.
Q.41 Difference between Mass and Weight.
Ans.
| Mass | Weight |
| i)The quantity of matter in body is called mass. | i)The force of attraction between body and earth is called weight. |
| ii)It is a scalar quantity. | ii)It is a vector quantity. |
| iii)It is denoted by “m” . | iii)It is denoted by ‘w’ . |
| iv)The unit of the mass is kilogram. | iv)The unit of the weight is Newton. |
| v)Mass cannot be zero. | v)Weight can be zero. |
| vi)Mass is measured by ordinary balance . | vi)Weight is measured by spring balance. |
| vii)m = F/a . | vii) w = mg |
Q.42 What is Tension. Write its unit.
Ans Tension:
Tension is a force , which is equal to the weight of body opposite in direction. Tension and weight
Of the body all ways acting in opposite direction. The unit of tension is Newton.
Q.43 What is the Law of Conservation of Momentum.
Ans. Law of Conservation of Momentum:
This law states that when two or more bodies collies with one another the total momentum
Of the system remains same provided no external force acts upon them.
Q.44 What is Friction?
Ans: Friction:
The force which resists the motion of one surface on another surface on another is called friction.
Q.45 Write the method to reduce the Friction.
Ans: following method are used to reduce the friction.
We can reduce the friction by polishing the parts of the machine.
We can reduce the friction by using the ball bearings.
We can reduce the friction by making the pointed shape of the front of the high speed vehicles aeroplans and ships.
We can reduce the friction by use of oil or grease.
Q.46 Explain the Rolling friction and Sliding Friction.
Ans. Rolling friction and Sliding Friction:
When a body moves with the help of wheels the friction in this case is called rolling friction.
The opposite friction of moving body from one surface of the body to surface on the body is called sliding friction.
Q.47 What are disadvantages of friction.
Ans. Disadvantages of friction:
Energy is wasted due to friction.
Due to the friction moving parts of machines become where and tear.
Q.48 What is Circular Motion? Give one example.
Ans. Circular Motion:
When a body moves in a circle then its motion is called circular motion e.g motion of a bicycle in
a Circle.
Q.49 What is Centripetal Force? Write its Formula.
Ans. Centripetal Force:
A force which acts on an object moving in a circle and is directed towards the center of the circle is called centripetal force.
Formula of centripetal force is given as
Fc = mv2/r
Q.50 What is Centrifugal Force? Write its Formula.
Ans. Centrifugal Force:
It is that force which is equal in magnitude to the centripetal force but opposite in direction is
called centrifugal force.
Formula of centripetal force is given as
Fr = mv2/r
Q.51 What are the parallel forces Define its types.
Ans. parallel forces:
If a number of forces acting on a body in such a way that their points of action are different but
lines of action are parallel to each other then these force are called parallel forces.
Types of parallel forces:
There are two types of parallel forces.
Like parallel force
Un- Like parallel force
Like parallel force:
If the direction of the parallel forces is the same then these type of the forces are called Like
parallel forces.
Un- Like parallel force.
If the direction of the parallel forces are opposite to one another then these types of the forces are called Un-Like parallel forces
Q.52 What is resolution of force?
Ans. Resolution of force:
Division of its components are called resolution of a force . Normally a force can be resolved into
two components. First component along x-axis is called Horizantal component and the second
component along y-axis is called the vertical component of a force.
Q.53 What is Torque or Moment of a force. Write its unites.
Ans. Torque or Moment of a force:
The turning effect of the force is called torque or Moment of a force.
Unit of the Torque or momentum of a force :
In SI unit of the torque or moment of force is Newton-meter (N.m).
Q.54 What factors depend on the torque .Write the formula of the torque.
Ans: Factors depend on torque:
There are two factors, which depend on the torque.
Magnitude of the force.(F)
Moment arm ®
These two factors are directly proportional to the producing torque. if troque is denoted by T.so we write.
T =F x r
Q.55 What is the centre of gravity. Give two examples.
Ans. Centre of Gravity
It is that point in a body where the whole weight of the body acts is called centre of gravity of
that body . e.g
Centre of gravity of uniform rod is centre of the rod
Centre of gravity of the sphere is centre of the sphere.
Q.56 What is Couple?
Ans. Couple:
When two equal, opposite and parallel forces act at two different points of the same body, they
form a couple. e.g opening nut of the tyre mechanics applies a couple
Q.57 What is Equilibrium?
Ans. Equilibrium:
If no net force is acting on the body then the body is said to be in equilibrium e.g. the book
Lying on the table.
Q.58 State the conditions of the equilibrium?
Ans. Conditions of the equilibrium:
There are two conditions of equilibrium
i) First conditions of the equilibrium:
There are two conditions states that if sum of all the forces acting on the body is equal
to zero then the body will be in equilibrium mathematically, we can write as:
F = 0
ii) Second Conditions of the Equilibrium:
The second conditions states that if algebraic sum of all the torques acting on a body equal to zero
then the body will be equilibrium.
Mathematically, We can write as:
= 0
For a complete equilibrium then it should be:
F = 0 and = 0
Q.59 How many states of the Equilibrium. Define each with example.
Ans. States of Equilibrium:
There are three states of equilibrium.
Stable equilibrium
Un-stable equilibrium
Neutral equilibrium
Stable Equilibrium:
It is that state of the equilibrium in which the body comes back its original position when
Set free after slightly lifting from one side. On lifting, the centre of the gravity of the body is raised up as compared to the initial position. e.g. A wooden rectangular block.
Un-stable Equilibrium:
it is that state of the equilibrium which if the position of the body is disturb it dose not come back its original position of the body is disturb it dose not come back to its original position. In such a case the centre of gravity is lowered than its original e.g. Free falling a wooden rectangular block.
Neutral Equilibrium:
It is that type of the equilibrium in which after disturbance, the body again comes to rest position of its centre of gravity dose not change. e.g. A ball lying on the table.
Q.60 What are Rigid Body and axis of Rotation.
Ans. Rigid Body:
A Rigid Body is the one that is not deformed by force or forces acting on it.
Axis of Rotation:
Consider a rigid body rotating about a line The particles of the body move in circles with lying on
this line. This line is called the axis of the body.
Q.61 State Principle of Moments.
Ans. Principle of Moments:
According to this to principle, “a body is balanced if the sum of clockwise moments acting
on the body is equal to the sum of anticlockwise moments acting on it”.
Q.62 Describe the types of Torque or Moment of Force.
Ans. Types of Torque Moment or of Force:
There are two types of torque of moment of force.
1)Clockwise moment. 2)Anti clockwise moment
Clockwise moment.
That torque which is produced in the clockwise direction is called clockwise moment.
Anti clockwise moment.
That torque which is produced in the Anti clockwise direction is called Anti clockwise moment.
Q.63 What is Centre of Mass.
Ans. Centre of Mass
Centre of Mass of a system is such a point where an applied force causes the system to move with
Out rotation.
Q.64 What is force of Gravitation?
Ans. Force of Gravitation:
In the universe there is a force due to which every body of the universe attracts every other body which is called force of gravitation.
Q.65 State the Newton’s law of Gravitation?
Ans. Newton’s law of gravitation:
This law states that every object in the universe attracts every other object with a force, which is Directly proportional to the product of their masses and inversely proportional to the square of thedistance between their centre.
Q.66 Write the values of G, M & R?
Ans. G = 6.67x10-11Nm2Kg-2 M = 6x1024Kg R = 6.4x106m
Q.67 What are artificial satellites ?Also write the name of natural satellite of our earth.
Ans. Artificial satellite:
It is that object which is used for communication and space research revolve around the earth
under the force of gravity which provides the necessary centripetal force .The orbital speed of the
satellite is 7.9 kms-1. Moon is a natural satellite of our earth.
Q.68 What is height of the Geo satellite from the surface of the earth? What is its velocity with respect to earth.
Ans. The height of the Geo Stationary satellite is about 42.300 km from the surface of the earth
Its velocity with respect to earth is zero.
Q.69 What is Global positioning system (GPS).What is its function.
Ans. Global Positioning System (GPS):
It is a satellite of navigation system. It helps us to fine the exact position of an any where of the
land on the sea or in the air . GPS consist of 24 earth satellite These satellites revolve around the
earth twice a day with a speed of 3.87 km s-1.
Q.70 What is a work Write its unit.
Ans Work :
The product of force and distance covered in direction of the force is equal to the work done. In
S.I unit of work is Joule .If work is denoted by W, force by F and distance by S then we can
write W=F.S
Q.71 What is Energy .Write its unit.
Ans. Energy:
The ability of a body to do work is called energy is joule.
Q.72 What is Kinetic Energy? Write its formula.
Ans. Kinetic Energy:
It is that energy which is produced due to motion is called kinetic energy.
Its formula is given as:- K.E = 1\2 mv2
Q.73 What is Potential Energy ? Write its formula.
Ans Potential Energy:
Energy of a body due to its height from the surface of the earth is called Potential Energy.
Its formula is given as :- P.E = mgh
Q.74 What are the forms of Energy?
Ans Forms of Energy:
1)Mechanical Energy 2)Heat Energy 3)Electrical Energy 4)Sound Energy
5)Light Energy 6)Chemical Energy 7)Nuclear Energy
Q.75 What is Mass - Energy Equation ?Write its formula .
Ans Mass-Energy Equation:
Einstein’s gave the mass energy equation . Its formula is given below :
E = mc2
Q.76 What is Efficiency .Write its formula .
Ans Efficiency:
The ratio of the useful work done by a machine to the work done on the machine is called
efficiency of the machine. The formula of efficiency is given as :
Efficiency = Output
Input
Usually Efficiency is calculated in percentage .Therefore we can write
Percentage Efficiency = Output x 100
Input
Q.77 What is Power ? Write its formula and unit .
Ans Power :
The rate of doing work with respect the time is called Power.
Power = Work
Time
In the S.I unit of Power is watt .
Q.78 What is Density ? Write its formula.
Ans Density:
Density of a substance is defined as its mass per unit volume .
Density = mass of a substance , d = m
volume of a substance v
Q.79 What is Pressure .Write its formula and unit .
Ans. Pressure:
The force exerted perpendicularly on unit area of an object is called Pressure.
Pressure = Force , P = F
Area A
In the S.I unit of Pressure is Newton Per Square meter (Nm-2) . It is also called Pascal.
Q.80 What is Stress and Strain? Write its units .
Ans. Stress:
Stress is the force that acts on the unit area of an object and thus changes its shape or size.
In the S.I unit of stress is Newton Per Square meter (Nm-2)
Strain:
It is defined as the change in the shape of an object caused due to stress. Strain has no unit.
Q.81 Define the Hooke’s Law?
Ans. Hooke’s Law:
It states that within the elastic limit of an object , the strain produced in an object is directly
proportional to the applied stress.
Q.82 State the Pascal’s Law.
Ans. Pascal’s Law:
This law states that if pressure is exerted on a liquid , the liquid distributes it equally in
all directions.
Q.83 State the Archimedes Principle.
Ans. Archimedes Principle:
It states that when an object immersed in a liquid, the liquid exerts a buoyant force on the
object which is equal to the weight of the liquid displaced by the object .
Q.84 State the Principle of Flotation:
Ans. Principle of Flotation:
According to this Principle ‘ A floating object displaces a fluid having weight equal to
the weight of the object.
Q.85 What is Young’s Modulus? Write its Equation.
Ans Young’s Modulus:
Tensile stress divided by strain is called Young’s Modulus .It is denoted by “Y”.
Its formula can written as: Y = F x L
A x L
Q.86 What is Elasticity.
Ans Elasticity:
The property of a body to restore its original size and shape as the deforming force
ceases to act is called elasticity.
Q.87 What is Heat? Write its unit?
Ans Heat:
It is a form of energy which is transferred from one body to the other due to the
difference of temperature between them. The unit of Heat is ‘Joule’.
Q.88 What is Temperature?
Ans Temperature:
It is the degree of hotness and coldness of a body.It can be measured in three different scales.
Q.89 For what scales are used to measure the Temperature?
Ans Scales to measure the temperature:
There are three scales are used to measure the temperature.
i)Fahrenheit Scale ii)Celsius Scale iii)Kelvin Scale
Q.90 What is Specific Heat? Write its unit. Also write the specific heat of water.
Ans Specific Heat:
The quantity of heat is required to change temperature of 1kg mass of a substance by one
Kelvin is called Specific Heat.
The unit of specific heat is Joule per Kilogram Per Kelvin (Jkg-1K-1).
The specific heat of water is 4200 Jkg-1K-1.
Q.91 What is Latent Heat of Fusion .Give one example.
Ans. Latent Heat of Fusion:
The quantity of heat required to change 1kg of a solid substance to liquid state without
changing the temperature is called latent heat of fusion. e.g. Latent Heat of Fusion
of Ice is 336000 Jkg-1.
Q.92 What is Latent Heat of Vaporization. Give one example.
Ans. Latent Heat of Vaporization:
The amount of heat needed to change 1kg of a liquid to vapor or gaseous state at a
fixed temperature is called Latent heat of Vaporization. e.g. Heat of Vaporization
of water 2,60,000 Jkg-1.
Q.93 What is the Evaporation?
Ans. Evaporation:
It is the changing of a liquid into vapors (gaseous state) from the surface of the liquid
without heating it.
Q.94 What factors depend upon the rate of Evaporation?
Ans. Factors Affecting on Evaporation:
1) Temperature 2) Surface Area 3) Nature of Liquid 4) Wind
Q.95 How many methods are used for the transmission of heat. Also define them.
Ans. Methods for the Transmission of heat:
There are three methods for the transmission of heat.
1)Conduction 2)Convection 3)Radiation
1) Conduction:
It is the process in which heat is transmitted from one body to another by the interaction of
molecules and electrons.
2) Convection:
It is that process of transfer of heat in which transmission of heat is due to the actual
movement of the molecules of the substance from one place to the other.
3) Radiation:
It is that process of transfer of heat energy reaches in the form of waves from one place to
the other without effecting the medium on its way.
Q.96 What is the importance of Conduction in our daily life?
Ans. Importance of conduction:
Normally metals are the good conductor of heat and non metals like wood or plastic are the
bad conductor of heat. Therefore the cooking utensils are made of metals and wood or
plastic is used for spoon handles. Wood or plastic being insulators don’t allow the heat
transfer and metallic vessels are preferred for freezing purpose. Air is a good insulator of
heat. Those object which can hold air in them behave as insulators. e.g fur, wood dust etc.
Q.97 What is the importance of the Convection in daily life ?
Ans: Importance of Convection in daily life:
Geysers in our houses work on convection principal. Water in the boiler is heated by convection and reaches the upper portion of the tank .Cold water from the water tank replaces the hot water .
Convection may take place in any liquid or gas. Ventilation of air in houses is only possible by convection .
To speed up natural convection ,fans pumps are used which is known as the forced convection.
WRITTEN BY: SIR GHALIB ABBAS
Ph: 03346718817 100% PASSED
COMPOSED BY: MUHAMMAD RASHID UL HASSAN SAEEDI
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