Motion.pptx

Chapter 1, Motion for class 9th

1. Chapter-1: motion Presented by: Hraday Narayan Pandey

2. Contents Rest and Motion Types of motion Terms used to define motion Various graphs related to motion Equations of motion

3. Rest and Motion Rest: An object is said to be at rest if it does not changes its position with time. Motion: An object is said to be in motion if it changes its position continuously with time.

4. Types of motion According to state of motion Uniform Motion: A body is said to be in state of uniform motion if it travels equal distances in equal intervals of time. Non-uniform Motion: A body is said to be in state of non-uniform motion if it travels unequal distances in equal intervals of time.

5. Terms used to define motion Distance and Displacement Speed and velocity Acceleration

6. Distance : The total length of the path covered by an object from its initial position to its final position is called distance. It is a scalar quantity. Distance never decreases with time It is always positive Displacement : The shortest length of the path from initial position to final position is called displacement of an object. It is a vector quantity. It can be positive, negative and zero. Note: In case of motion: Distance is always greater than or equal to displacement. i.e. distance ≥ displacement

7. Speed : The distance travelled by an object per unit time is called speed of an object. It is a scalar quantity. Velocity : The displacement of an object per unit time is called velocity of an object. It is a vector quantity.

8. Acceleration: The rate of change in velocity is called acceleration. It is denoted by ‘a’. a=Change in velocity/Time taken It is a vector quantity. The SI unit of acceleration is ms −2 When the direction of acceleration is in the direction of motion of an object, the acceleration is said to be positive acceleration. When the direction of acceleration is opposite to the direction of motion of an object, the acceleration is said to be negative acceleration (deceleration or retardation).

9. Various graph related to motion Distance-Time graph: Slope of s-t graph gives speed of an object .

10. Velocity-Time graph: Slope of v-t graph gives acceleration. Area under the v-t graph gives displacement.

11. Acceleration-Time graph: Area of a-t graph gives velocity.

12. Equations of motion The motion of an object moving with uniform acceleration can be described with the help of three equations called equations of motion. Equation for velocity time relation(1 st equation of motion) v = u + at Equation for position-time relation(2 nd equation of motion) s = ut + ½at² Equation for position-velocity relation (3 rd equation of motion) v² = u² + 2as

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