Question

Ch 8 motion class 9 notes Science ​

Answer 1

Answer:

An object is said to be in motion when its position changes with time.

We describe the location of an object by specifying a reference point. Motion is relative. The total path covered by an object is said to be the distance travelled by it.The shortest path/distance measured from the initial to the final position of an object is known as the displacement.

Uniform motion: When an object covers equal distances in equal intervals of time, it is said to be in uniform motion.Non-uniform motion: Motions where objects cover unequal distances in equal intervals of time.

Speed: The distance travelled by an object in unit time is referred to as speed. Its unit is m/s.Average speed: For non-uniform motion, the average speed of an object is obtained by dividing the total distance travelled by an object by the total time taken.

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Velocity: Velocity is the speed of an object moving indefinite direction. S.I. unit is m/s.

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Acceleration: Change in the velocity of an object per unit time.Graphical representation of motions

(i) Distance-time graph

For a distance-time graph, time is taken on x-axis and distance is taken on the y-axis.

[Note: All independent quantities are taken along the x-axis and dependent quantities are taken along the y-axis.]