MOTION ppt

1. MOTION

2. INTRODUCTION • We use the word ‘REST’ very often. For example, when someone is doing no work or lying on the bed, we say that the person is at rest. This means the person is not moving. • Scientifically, we say an object is at rest when the position of the object does not change with time , with respect to its surroundings. • Similarly, ‘MOTION’ is defined as the change in position of an object with time, with respect to its surroundings. Cars, cycles, buses, trucks etc. running on the road. Birds flying in the sky. Fishes swimming in the water. All these objects are in motion. Very large objects like planets, stars and galaxies (building block of universe) are in motion.

3. TYPES OF MOTION • LINEAR MOTION : A body has linear motion if it moves in a straight line or path. Examples-1.Motion of a moving car on a straight road 2.Motion of a ball dropped from the roof of a building • CIRCULAR OR ROTATIONAL MOTION : A body has circular motion if it moves around a fixed point. A vertical line passing through the fixed point around which the body moves is known as axis of rotation. Examples-1.Motion of an electric fan 2.Motion of merry-go-round 3.Motion of a spinning top • VIBRATORY MOTION : A body has vibratory motion if it moves to and fro about a fixed point called mean position or equilibrium position). Examples-1.Motion of a pendulum of a wall clock 2.Motion of a child swinging in a swing 3.Motion of a simple pendulum

4. Motion can be described in terms of the (i)Distance moved or the(ii)Displacement . • DISTANCE -The length of actual path between the initial position and the final position of a moving object in the given time interval is known as distance. • DISPLACEMENT-Theshortest distance between the initial position and the final position of a moving object in the given interval of time from initial position to the final position of the object is known as the displacement of the object.

5. UNIFORM MOTION & NON UNIFORM MOTION • UNIFORM MOTION : The motion of an object is uniform if (i) it moves along a straight line and (ii) it covers equal distances in equal intervals of time , however, small these intervals may be. Example-Movement of clock’s hand and pendulum. • NON UNIFORM MOTION: The motion of an object is said to be non-uniform if it covers unequal distances in equal intervals of time , however, small these intervals may be. Example - A bus moving on a crowded road , a car on a hilly track.

6. SPEED Speed of an object is defined as the distance travelled by it per unit time. Speed of an object tells us how fast the object moves. SPEED = DISTANCE or v = S TIME t S.I unit of speed is metre/second (ms-1 ) In CGS System,unit of speed is centimetre/second(cms-1) IN OUR DAILY LIFE ,THE SPEED OF MOVING BUSES, CARS, TRAINS, AND AEROPLANES IS EXPRESSED IN KILOMETRE/HOUR (kmh-1)

7. TYPES OF SPEED • UNIFORM SPEED OR CONSTANT SPEED – If a moving body covers equal distances in equal intervals of time, then the speed of the body is said to be a uniform speed. LIGHT TRAVELS WITH A CONSTANT SPEED IN A MEDIUM THE VALUE OF CONSTANT SPEED OF LIGHT IN AIR IS 3 108. • NON UNIFORM OR VARIABLE SPEED - If a moving body covers unequal distances in equal intervals of time , then the speed of the body is said to be non-uniform or variable speed. • AVERAGE SPEED – Average speed of a moving body is defined as the ratio of the total distance travelled by it to the total time taken by it. vav = Total distance travelled Total time taken

8. VELOCITY(Speed with direction) Velocity of an object is defined as the displacement of the body per unit time. Velocity of an object tells us how fast the object is moving and in which direction it is moving. Velocity= Displacement orv = S Time t S.I unit of velocity is metre /second (ms-1) In CGS System, unit of velocity is centimetre/second (cms-1) COMMONLY USED UNIT OF VELOCITY IS kilometre/hour (kmh-1 )

9. TYPES OF VELOCITY • UNIFORM VELOCITY OR CONSTANT VELOCITY – Velocity of an object is said to be an uniform velocity if it covers equal displacements in equal intervals of time. • NON-UNIFORM VELOCITY OR VARIABLE VELOCITY - Velocity of an object is said to be a non- uniform or variable velocity if it covers unequal displacements in equal intervals of time. • AVERAGE VELOCITY – When the speed of an object changes with time along a straight line, then the average velocity is calculated as Average Velocity (vavg ) = Total Displacement of the body Total time taken

10. ACCELERATION Acceleration of a body or an object is defined as the change in velocity per unit time. Acceleration tells us by how much amount the velocity of a body changes in unit interval of time. Acceleration (a) = Change in velocity = v-u Time taken t SI unit of acceleration is ms -2 and CGS unit is cms-2; other unit of acceleration is kmh-2 POSITIVE ACCELERATION- If the velocity of an object increases with time in the direction of the motion of the object, then the acceleration of the body is known as positive acceleration. NEGATIVE ACCELERATION- If the velocity of an object decreases with time, then the acceleration of the object is known as negative acceleration.

11. TYPES OF ACCELERATION • UNIFORM ACCELERATION - If the velocity of an object changes by an equal amount in equal intervals of time, then the acceleration of the object is known as uniform acceleration. Example- Motion of an object falling freely from the top of the building, Motion of a ball rolling on a smooth inclined plane. • NON – UNIFORM ACCELERATION- If the velocity of an object changes by an unequal amount in equal intervals of time, then the acceleration of the object is known as non-uniform or variable acceleration. Example- Motion of a bus leaving or entering the bus stop , Motion of a bus crowded road.