■ Motion – Study Notes
1. Introduction
•Motion: Change in the position of a body with respect to time.
•If a body remains in the same position, it is said to be at rest.
•Described using distance, displacement, speed, velocity, and acceleration.
2. Types of Motion
•Translatory Motion: Object moves from one point to another.
•- Rectilinear Motion: Along a straight line.
•- Curvilinear Motion: Along a curved path.
•Rotatory Motion: Object moves about a fixed axis (e.g., Earth’s rotation).
•Oscillatory/Vibratory Motion: To and fro motion about a fixed point (e.g., pendulum).
•Random Motion: No definite path (e.g., gas molecules).
3. Distance and Displacement
•Distance: Total length of the path travelled (scalar).
•Displacement: Shortest distance from initial to final position (vector).
4. Speed and Velocity
•Speed: Distance travelled per unit time (scalar). Average Speed = Total Distance ÷ Total Time.
•Velocity: Displacement per unit time (vector). Average Velocity = Displacement ÷ Time.
5. Acceleration
•Acceleration: Rate of change of velocity with respect to time.
•Types:
•- Uniform Acceleration: Equal velocity changes in equal intervals.
•- Non-uniform Acceleration: Unequal changes in equal intervals.
•- Retardation (Deceleration): Negative acceleration.
6. Equations of Uniformly Accelerated Motion
•v = u + at
•s = ut + 1/2 at²
•v² = u² + 2as
•Where: u = initial velocity, v = final velocity, a = acceleration, t = time, s = displacement.
7. Graphical Representation of Motion
•Distance–Time Graph: Slope gives speed.
•Velocity–Time Graph: Slope = Acceleration, Area = Displacement.
•Acceleration–Time Graph: Area = Change in velocity.
8. Uniform Circular Motion
•Motion in a circle with constant speed but changing direction.
•Acceleration is always directed toward the centre → Centripetal Acceleration.
•Centripetal Force: F = mv²/r.
9. Key Points to Remember
•Motion can be linear, circular, oscillatory, or random.
•Distance = scalar, Displacement = vector.
•Speed vs. Velocity: Speed has no direction, Velocity has.
•Equations of motion apply only under constant acceleration.
