Studied by 9 people
(SA) State the Universal Law of Gravitation
The force of attraction between any two bodies in the universe is directly proportional to the product of the masses and inversely proportional to the square of the distances between them.
(F) Gravitational Force
F = Gm₁m₂/r²
(V) Universal Gravitation Constant
6.67 × 10⁻¹¹ Nm²/kg²
(LA) Applications of Universal Law of Gravitation
Force that binds us to the earth
Motion of moon around the earth
Motion of planets around the sun
Waves are caused by the gravitational attraction by the moon
Rivers flow on earth due to the gravitational pull on the river by the water.
(D) Centripetal Force
The force that keeps a body in circular motion and acts towards the centre
(V) Mass of the Earth
6 × 10²⁴ kg
(V) Radius of the Earth
6.4 × 10⁶ m
(D) Free Fall
The motion in which a body falls towards the earth only infludenced by the earth’s gravitational force.
(F) Value of g
g = GM/R²
(SA) Differentiate between mass and weight
Weight
The force with which the object is attracted towards the earth
It is a vector quantity
It changes from place to place
It is zero at the centre of the earth
SI Unit is Newton
Mass
The quantity of matter contained in a body
It is a scalar quantity
It does not change from place to place
It can never be zero
SI Unit is Kilogram
(SA) How does the value of g change.
The value of g decreases as we go further down under the arth and it becomes zero at the centre.
(F) What is used to measure weight of the body
Spring Balance
(F) What is used to measure mass
Physical Balance / Pan Balance / Beam Balance
(F) Pressure
Pressure (P) = Thrust (T) / Area (A) N/m2
(D) Thrust
The force acting on an object perpendicular to the surface
(D) Pressure
Pressure is the force acting perpendicularly on a unit area of an object.
(LA) Applications of Pressure
Handles and straps of bags are made broad to reduce load
Base of buildings are made broad to reduce force on the ground.
Wheels of tractors are made broad to avoid is damaging the field and sinking into the ground.
Nails , Screws and knives are made pointy at the end to make it easier to penetrate.
(SA) How do fluids exert pressure?
Fluids exert pressure on the walls of the container they are enclosed in , in all directions.
(D) Buoyancy
Tendency of the liquid to exert an upward force on an immersed object.
(D)Buoyant Force
The upward force which a liquid applies on an. object immersed in it.
(SA) Factors Affecting Buoyancy
It is directly proportional to the density of the object
It is directly proportional to the volume of object immersed in the object.
(D) Density
Denisty is defined as mass per unit volume.
(SA) State the Archemedies Principle
When an object is fully or partially immersed in a liquid it experiences a buoyant force or upthrust which is equal tot he weight of the liquid displaced by the object.
(SA) Applications of Archimedes Principle
Designing ships and submarines
Lactometer - device used to determine the purity of milk.
Hydrometer - device used to determine the density of a liquid.
(F) Buoyant Force
Buoyant Force = Weight of liquid displaced by the object.
(D) Work
Work can be defined as the product of force and displacement
(F) SI unit of Work
Joule
(D) Postive Work
When force and dispalcement are in the same direction psitiive work is done
(D) Negative Work
When force and displacement are in opposite directions negative work is said eto be done.
(D) Zero Work
When the force applied is perpendicular to the direction of force applied the work doen is said to be negative.
(D) Energy
Energy can be defined as the capacity to do work
(F) 1kJ = x J
10³ J
(SA) State the work energy theorem
Whenever a force is applied on the body and i gets displaced , work done is equal to the change in kinetic energy of the body.
(D) Kinetic Energy
The energy which is possessed by an object by virtue of its motion is called kinetic energy.
(D) Potential Energy
The energy possessed by the body due to its change in position or shape is called potential energy.
(SA) State the law of conservation of energy.
Energy can neither be created nor destroyed it can be converted from one form to another. The total amount of energy for an isolated system in the universe is always constant.
(D) Power
The rate of doing owrk or the rate at which energy is transferred or used or transformed to other form is called power.
(F) SI Unit of Power
Watt in honour of James Watt
(F) Average Power
Average Power = Total Energy Consumed / Total Time Taken
1 Horse Power = y Watts
746
(D) Sound
Sound is a form of energy which produced a sensation of hearing in our ears.
(D) Mechanical Waves
Waves that require a medium to travel
(SA) Propagation of Sound
When an object vibrates it exerts a force on the particle of the medium displacing it from its equilibrium position.
The displaced particle displaces it’s adjacent particle and comes back to rest
This process continues till the sound reaches our ears
(D) Compressions
Compression is part of the longitudinal wave in which the particles of the medium are closer to one another and it is the region of high compression.
(D) Rarefactions
Rarefaction is the part of a longitudinal wave in which the particles of the medium are farther apart than they normally are and it is the region of low pressure.
(D) Longitudinal Wave
Longitudinal waves have individual particles of the medium move in a direction parallel to the direction of propagation of the disturbance.
(D) Transverse Wave
The individual particles move about its mean position in a direction perpendicular to the direction of wave propagation is called a transverse wave.
(D) Wavelength
The distance between two consecutive rarefactions or two consecutive compressions.
(D) Frequency
The number of oscillations of the wave in one second.
(F) SI unit of Frequency
Hertz ( Heinrich Rudolf Hertz)
(D) Time Period
Time taken by two consecutive rarefactions or compressions to cross a fixed point is known as time period. or the time required to produce one complete oscilation
(F) Time Period
Time Period = 1/ Frequency
(D) Amplitude
The maximum displacement of a particle of the medium from it’s mean position is known as amplitude.
(D) Speed
Distance travellled by the wave in one second
(F) Speed of Sound
V = µλ
(D) Loudness
MEasure of sound energy reaching the ear per second. The greater the sound energy the louder the sound will appear to be.
(D) Intensity
The amount of sound energy passsing each second through a unit area.
(F) SI unit of inensity
W/m2
(D) Pitch of Sound
Pitch of the sound is directly realted to the frequency of the sound.
Speed of sound in air
340 m/s
(D) Reflection of Sound Wave
The bouncing back of sound when it strikes a hard surface
(D) Echo
The repetition of sound caused by multiple soudn waves is called echo.
(D) Reverberation
The persistance of sound due to multiple repeated reflections is known as reverberation.
(LA) Applications of multiple reflections of sound
Megaphone - large cone shaped device used to amplify the voice of a person. The cone shaped walls cause successive reflections and prevent the sound from spreading making it heard over long distances
Stethoscope - multiple reflections occur in the stethoscope tube causing the sound to reach the doctors ears.
Sound board - curved or concave boards are placed in big halls to spread the sound evenly across the hall.
(D) Infrasonic Sound
Sound waves with frequency less than 20 Hz
(F) Hearing range of elephants and rhino
5 Hz
(F) Ultrasonic hearing range of dogs
5000 Hz
(F) Which animals can produce utrasonic sound
Dolphins , bats , porpoises
Applications of Ultrasound
Echocardiography
Ultrasonography
Break down kidney stones
Clean parts. by putting in liquid
Detect cracks and flaws in metals
(LA) Differentiate between Distance and Displacement
Distance
The length of the actual path travelled by the object n given interval of time
It is a scalar quantity
It is always positive
It depends on the path travelled by the object
It is always equal or greater than displacement
Displacement
The shortest distance between initial and final position of an object moving in a particular direction
It is always negative.
It can be positive , negative or zero
It only depends on the initial and final position
It is always equal or less than the distance
(D) Uniform Motion
The motion of an object is considered to be uniform if it covers equal disrtances in equal intervals of time
(D) Non Uniform Motion
The motion of an object is considered to be mom uniform if it does not cover equal distances in equal intervals of time
(D) Uniform Speed
If the object is said to have uniform speed if it cover equal distance in equal intervals of time
(D) Non Uniform Speed
An object is said to be in non uniform speed if it covers unequal distance in equal intervals of time.
(D) Average Velocity`
It is defined as the ratio of total displacement covered by a body to the total time taken by it.
(D) Resultant Force
The resultant force is when a force acting on a body produces the same effect as that produced by a number of forces.
(D) Inertia
The property of the body by virtue of which it opposes any sort of change in it’s state of motion.
(D) Momentum
The product of mass and velocity of the object of a body. It is a vector quantity
(D) First Law of Motion
A body continues to be either in state of rest or uniform motion along a straight line unless an external force is applied on it.
(D) Second Law of Motion
The rate of change of momentum is directly proportional to the applied force and take place in the same direction as the applied force.
(D) Third Law of Motion
It state that to evry action there is an equal and opposite reaction. Action and reaction forces are equal but act in the opposite direction.
(D) Impulse
it is the change in momentum of the body.
(F) Impulse
Ft = mv - mu
