Notes for Class 9 Science Chapter 7 Motion is prepared and uploaded for reference by academic team of expert members of Param Himalaya. Get Notes of all chapters of NCERT class 9 Science from Param Himalaya.
Definition of Reference Point or Origin :
A reference point is a point that is used to determine the position , speed or direction of an object that is in motion.
Example :
1. A tree on the side of the road that helps a driver understand how fast they are going.
2. A landmark on a map that helps a hiker understand their location.
3. A stationary car that helps a pedestrian understand how fast they are walking.
My school is located at distance of 10 km north of my house . Here , House is the reference point is used for describing where is my house located.
Definition of Motion or Rest with Example -
When the position of an object doesn't change with respect to reference point and time then object is said to be at rest.
When the position of an object change with respect to reference point and time then object is said to be in motion.
Type of motion
1. Linear motion : A body has linear motion if it moves along a straight line or path.
Example :
-motion of a moving car on a straight road
-motion of ball dropped from the roof of a building.
2. Circular / Rotational motion : A body has circular motion if it moves around a fixed point.
Example :
- motion of an electric fan
- motion of merry-go-round.
- an athlete Moves along the circular track.
3. Oscillatory / Vibratory motion :
- a body has vibratory motion if it moves to and fro about a fixed point ( called mean position or equilibrium position ) .
Example :
- motion of a pendulum of a wall clock.
- motion of a child swinging in a swing.
- motion of a simple pendulum.
Define Physical quantity and its Types
1. Scalar quantity :
It is the physical quantity having its own magnitude but no direction.
Scalar quantity are either positive or zero. They do not have negative values.
Example : Distance , speed
2. Vector quantity:
It is the physical quantity that requires both magnitude and direction.
Vector physical quantities are either positive , negative or zero.
Example : Displacement , Velocity