Motion Class 9 Science — Revision Notes
This chapter covers motion in one dimension including distance, displacement, speed, and velocity. Students learn about graphs of motion and equations of m
TL;DR: This chapter covers motion in one dimension including distance, displacement, speed, and velocity. Students learn about graphs of motion and equations…
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This chapter covers motion in one dimension including distance, displacement, speed, and velocity. Students learn about graphs of motion and equations of m
Distance and Displacement
- Distance is total path length traveled (scalar quantity)
- Displacement is shortest path from start to finish (vector quantity)
- Distance always positive, displacement can be positive or negative
- Distance >= displacement for any motion
Speed and Velocity
- Speed = distance / time (scalar quantity)
- Velocity = displacement / time (vector quantity)
- Average speed = total distance / total time
- Average velocity = total displacement / total time
- Uniform velocity: velocity constant over time
Acceleration
- Acceleration = change in velocity / time = (v - u) / t
- Positive acceleration: velocity increasing
- Negative acceleration (deceleration): velocity decreasing
- Uniform acceleration: constant change in velocity
Equations of Motion
- v = u + at
- s = ut + 1/2 at^2
- v^2 = u^2 + 2as
- Valid only for uniform acceleration
Key Terms
- Velocity: Rate of change of displacement (vector quantity with direction)
- Acceleration: Rate of change of velocity
- Displacement: Shortest distance from initial to final position in specific direction
Frequently Asked Questions
Why is velocity called vector while speed is scalar?
Speed only has magnitude (how fast). Velocity has both magnitude and direction (how fast and which direction). Vectors require direction.
What does negative acceleration mean?
Negative acceleration (deceleration) means velocity is decreasing. Object is slowing down in the positive direction or speeding up in negative direction.
More Class 9 Science Revision Notes
- Matter in Our Surroundings
- Is Matter Around Us Pure
- Atoms and Molecules
- Structure of the Atom
- The Fundamental Unit of Life
- Tissues
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