Physics: Motion

PHYSICS CLASS IX CHAPTER - MOTION Important terms: Rest: An object is said to be at rest if it doesnot change its position with respect to (w.r.t) its surroundings with time. stationary object: not moving e.g. wall, a book on the table magnitude: How much (distance / quantity) Reference point: The specific pt. w.r.t motion of another moving body is measured. physical quantity: It is quantity in physics that can be measured. e.g. time, temp., mass, electric current, acceleration. Scalar quantity: It has only magnitude, no direction e.g. time, length, distance. Vector quantity: It has both magnitude as well as direction. e.g. displacement, velocity. Motion: A body is said to be in motion when its position changes Continuously w.r.t a stationary e.g. The position of a Car changes continuously etc. w.r.t object taken as reference point. stationary objects like houses, trees i.e. moving car is in motion. Distance Displacement The actual length of the It is the straight line (or indirect path covered by shortest) path b/w the initial a moving body irrespective point & final pt. along with of the direction. direction. sealar quantity vector quantity B B cannot be zero can be Zero. e.g. distance from 2km 4km e.g. displacement from A toc = 2km. 2km 4km A to C 24476km A C 2km displacement from A c 2km distance from A to A = 0 AtoA = 2nr A A