9th Sci. Chapter 1: Laws of Motion, Notes

Chapter 1: Laws of Motion, Notes

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✍🏻... विज्ञान विषयाच्या माहितीसाठी खालील⬇️ लिंकला🖇️ स्पर्श करा.🎸

👉🖊️  माहिती विज्ञानाची 🎷

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1. Motion & Relative Motion

Definition of motion: 

An object is said to be in motion if its position changes with respect to its surroundings; otherwise, it is at rest.

Motion is a relative concept. 

Ex: Flight of a bird and leaves flying through air represent motion, while a stationary train or a stone on a hill represents rest.

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2. Difference—Distance and Displacement

Many times distance is more than displacement.

Many times displacement is less than distance.

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Scalar vs. Vector:

Scalar Quantity: Has magnitude only (e.g., distance, speed, time).

Vector Quantity: Has both magnitude and direction (e.g., displacement, velocity, acceleration).

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3. Speed and Velocity

Formulas:

Units:

SI System: m/

CGS System: cm/s

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Effect of Speed and Direction on Velocity:

Velocity depends on both speed and direction. 

Velocity changes by:

• Changing speed while keeping direction constant.
• Changing direction while keeping speed constant.
• Changing both speed and direction simultaneously.

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4. Uniform and Non-Uniform Motion

Definition of Uniform Motion: An object covers equal distances in equal intervals of time.

Definition of Non-Uniform Motion: An object covers unequal distances in equal intervals of time (e.g., a vehicle moving through heavy traffic).

5. Acceleration

(where u = initial velocity, v = final velocity, and t = time)

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Types of Motion Based on Acceleration:

Uniform Acceleration: Velocity changes by equal amounts in equal time intervals.

Non-Uniform Acceleration: Velocity changes by unequal amounts in equal time intervals.

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Types of Acceleration:

1. Positive Acceleration: Velocity increases over time (acceleration is in the direction of velocity).
2. Negative Acceleration (Deceleration/Retardation): Velocity decreases over time (acceleration is opposite to the direction of velocity).
3. Zero Acceleration: Velocity remains constant over time.

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6. Graphical Representation of Motion

Distance-Time Graphs:

• Uniform Motion: A straight line (indicates direct proportionality between distance and time; the slope represents speed).
• Non-Uniform Motion: A non-linear curve.
• Velocity-Time Graphs:
• Uniform Velocity: A straight horizontal line parallel to the time axis.
• Uniform Acceleration: A straight line sloping upwards (indicates velocity changes equally in equal time intervals).
• Distance Covered: The area under the curve in a velocity-time graph equals the distance travelled by the object in that time interval.

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*आयुष्य म्हणजे अनुभव,प्रयोग आणि अपेक्षा यांचे समीकरण आहे.....* 

*कालचा दिवस म्हणजे अनुभव होता...*

 *आजचा दिवस प्रयोग असतो....* 

*आणि उद्याचा दिवस ही अपेक्षा असते....*

 *वाट्याला आलेल आयुष्य मर्यादित आहे, अनिश्चित आहे.....*

 *म्हणूनच कसलीही अपेक्षा न ठेवता जो जगत असतो तो ...... होतो!*

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