Question

please give the notes of ch-motion class-9​

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.
• Velocity: Velocity is the speed of an object moving indefinite direction. S.I. unit is m/s.
• Acceleration: Change in the velocity of an object per unit time.
• (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.]

• Uniform circular motion: When a body moves in a circular path with uniform speed, its . motion is called uniform circular motion

Explanation:

velocity time graph is also there along with their derivation. if u need then u can say me i will send u the pic

Answer 2

Answer:

Understanding Motion

Reference point and reference frame

To describe the position of an object we need a reference point or origin. An object may seem to be moving to one observer and stationary to another.

Example: A passenger inside a bus sees the other passengers to be at rest, whereas an observer outside the bus sees the passengers to be in motion.

In order to make observations easy, a convention or a common reference point or frame is needed. All objects must be in the same reference frame.