Motion

1. MOTION A body is said to be in motion when its position changes continuously with respect to a stationary object reference point. For example, when the position of a car changes continuously with stationary objects like houses and trees, etc., we say that the car is in motion. taken as respect to TYPES OF MOTIONS: A body can have three types of motions: (i) Translational motion (ii) Rotational motion and (iii) Vibrational motion ➢Translational Motion: A body has motion if a line joining any two points on the body remains parallel to itself throughout the motion of the body. Example: A bus moving on a straight road. translational ➢Rotational body has rotational motion if it moves around a fixed line called axis of rotation such that all constituting the body move simultaneously concentric circles having their centres on the axis of rotation. Example: Motion of the earth around the sun. Motion: A the particles along

2. ➢Vibrational Motion: A body has vibrational motion if it moves to and fro after regular interval of time about a fixed point called the mean position or the equilibrium position. Example: motion of pendulum of a wall clock . The meaning of both distance and displacement are important for studying the motion of bodies. DISTANCE AND DISPLACEMENT ➢Distance: The length of the actual paths between initial and final positions of a particle in a given interval of time is called distance covered by the particle. Distance is a scalar quantity (because it has magnitude only, it has no specified direction). ➢Displacement: The shortest distance from the initial position to the final position of the particle is called displacement. Displacement is a vector quantity (because it has magnitude as well as a direction). UNIFORM MOTION AND NON-UNIFORM MOTION ➢Uniform Motion: A body has a uniform motion if it travels equal distances in equal intervals of time. The distance-time graph for uniform motion is a straight line. ➢Non-Uniform Motion: A body has a non-uniform motion if it travels unequal distances in equal intervals of time. The distance-time graph for a body having non-uniform motion is a curved line.

3. SPEED, VELOCITY AND ACCELERATION ➢Speed: The distance travelled by a body per unit time is known as speed of the body. ????? =???????? ➢Average Speed: Average speed of a body is defined as the ratio of the total distance travelled by it to the total time taken. ??????? ????? =????? ???????? ????????? ➢Velocity: The displacement of a particle or body per unit time is called the velocity of the body. ????????(?) =???????????? ➢Average Velocity: It is the ratio of total displacement to the total time taken. ??????? ???????? =????? ???????????? For uniformly changing velocity, the average velocity can be calculated as follows: ??????? ???????? =??????? ???????? + ????? ???????? ???? ????? ???? ????? =∆? ∆? ???? ????? ???? 2 ➢Acceleration: Acceleration of a body is defined as the rate of change of its velocity with time. ?ℎ???? ?? ???????? ???? ????? ??? ?ℎ???? ???????????? =

4. ➢Uniform Acceleration: A body has a uniform acceleration if it travels in a straight line and its velocity increases by equal amounts in equal intervals of time. ➢Non-Uniform Acceleration: A body has a non-uniform acceleration if its velocity increases by unequal amounts in equal intervals of time. ➢Retardation (or Deceleration or Negative Acceleration ): If the velocity of a body increases, the acceleration is positive, and if the velocity of a body decreases, the acceleration is negative. A body is said to be retarded if its velocity is decreasing. Retardation is measured in the same way as acceleration, that is, retardation . Retardation is actually acceleration with the negative sign, +