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Class 9 Chapter 8 – Motion
 Movement of any object from one place to other in a uniform or non uniform speed is called Motion
 To describe the position of an object we need to specify a reference point called the origin.
 The simplest type of motion is the motion along a straight line.
 The shortest distance measured from the initial to the final position of an object is known as the displacement.
 As the object covers equal distances in equal intervals of time, it is said to be in uniform motion.
 As the object covers unequal distances in equal intervals of time, it is said to be in non uniform motion.
Graphical representation of motion
 Distance time graph
SPEED
 One of the ways of measuring the rate of motion of an object is to find out the distance travelled by the object in unit time. This quantity is referred to as speed.
 The SI unit of speed is meter per second represented by the symbol m s^{1} or m/s.
 The other units of speed include centimeter per second (cm s^{1}) and kilometer per hour (km h^{1}).
 To specify the speed of an object, we require only its magnitude.
AVERAGE SPEED
 The average speed of an object is obtained by dividing the total distance travelled by the total time taken.
VELOCITY
 The quantity that specifies both the speed and direction is called velocity.
 Velocity is the speed of an object moving in a definite direction.
 The velocity of an object can be uniform or variable.
 In case the velocity of the object is changing at a uniform rate, then average velocity is given by the arithmetic mean of initial velocity and final velocity for a given period of time.
Velocitytime graph
ACCELERATION
 Acceleration is a measure of the change in the velocity of an object per unit time.
 If the velocity of an object changes from an initial value ‘u’ to the final value ‘v’ in time ‘t’, the acceleration ‘a’ is, a = (vu)/t.
 This kind of motion is known as accelerated motion.
 The acceleration is taken to be positive if it is in the direction of velocity.
 The acceleration is taken to be negative when it is opposite to the direction of velocity.
 The SI unit of acceleration is m s^{2}.
 If an object travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time, then the acceleration of the object is said to be uniform motion.
 If an object can travel with nonuniform acceleration and if its velocity changes at a nonuniform rate then the acceleration is said to be Non uniform motion.
GRAPH OF MOTION
 To describe the motion of an object, we can use line graphs.
 In this case, line graphs show dependence of one physical quantity, such as distance or velocity, on another quantity, such as time.
 For uniform speed, a graph of distance travelled against time is a straight line.
EQUATIONS OF MOTION
 When an object moves along a straight line with uniform acceleration, it is possible to relate its velocity, acceleration during motion and the distance covered by it in a certain time interval by a set of equations known as the equations of motion.
 There are three such equations.
 Velocity Time Relation Equation v = u + at.
 Position Time Relation Equation s = ut + 1/2 at^{2}.
 Position Velocity Relation Equation 2as = v^{2 }– u2^{.}
 Where u is the initial velocity of the object which moves with uniform acceleration a for time t, v is the final velocity, and s is the distance travelled by the object in time t.
UNIFORM CIRCULAR MOTION
 When an object moves in a circular path with uniform speed, its motion is called uniform circular motion.
Course Curriculum

Lessons
 Chapter 1 – Matter in our surroundings
 Chapter 2 – Is matter around us pure
 Class 9 chapter 3 – Atoms & Molecules
 Class 9 Chapter 4 – Structure of the Atom
 Class 9 Chapter 5 – The fundamental unit of life
 Class 9 Chapter 6 – Tissues
 Class 9 Chapter 7 – Diversity in living organisms
 Class 9 Chapter 8 – Motion
 Class 9 Chapter 9 – Force and laws of motion
 Class 9 Chapter 10 – Gravitation
 Class 9 Chapter 11 – Work & Energy
 Class 9 Chapter 12 – Sound
 Class 9 Chapter 13 – Why do we fall ill
 Class 9 Chapter 14 – Natural Resources

Question Bank
 Class 9 Question Bank Chapter 1 – Matter in our surrounding
 Class 9 Question Bank Chapter 2 – Is matter around us pure
 Class 9 Question Bank Chapter 3 – Atoms and molecules
 Class 9 Question Bank Chapter 4 – Structure of the Atom
 Class 9 Question Bank Chapter 5 – The fundamental unit of life
 Class 9 Question Bank Chapter 6 – Tissues
 Class 9 Question Bank Chapter 7 – Diversity in living Organism
 Class 9 Question Bank Chapter 8 – Motion
 Class 9 Question Bank Chapter 9 – Force and laws of Motion
 Class 9 Question Bank Chapter 10 – Gravitation
 Class 9 Question Bank Chapter 11 – Work and energy
 Class 9 Question Bank Chapter 12 – Sound
 Class 9 Question Bank Chapter 13 – Why do we fall ill
 Class 9 Question Bank Chapter 14 – Natural Resources