Overview
This lecture explains the concepts of motion, including types of motion, measurement of speed and velocity, acceleration, graphical representation, equations of motion, and uniform circular motion.
Introduction to Motion
- Motion is when an object's position changes over time; at rest means no such change.
- Perception of motion depends on the observer's reference point or origin.
- Objects can move in straight lines, circles, rotate, or vibrate.
Describing Motion
- Position is described relative to a chosen reference point (origin).
- Distance is the total path length traveled, regardless of direction.
- Displacement is the shortest straight-line distance from initial to final position, considering direction.
Types of Motion
- Uniform motion: equal distances covered in equal time intervals.
- Non-uniform motion: unequal distances covered in equal time intervals.
Measuring Rate of Motion
- Speed = distance travelled / time taken; SI unit: m/s.
- Average speed = total distance travelled / total time taken.
- Velocity = speed with direction; average velocity = displacement / time.
- For changing velocity at a uniform rate: average velocity = (initial velocity + final velocity) / 2.
Acceleration
- Acceleration = change in velocity / time taken; SI unit: m/s².
- Uniform acceleration: velocity changes equally in equal intervals (e.g., free fall).
- Non-uniform acceleration: velocity changes unequally in equal intervals.
Graphical Representation of Motion
- Distance-time graphs:
- Straight line: uniform speed.
- Curved line: non-uniform speed.
- Velocity-time graphs:
- Straight parallel to time axis: uniform velocity.
- Slope represents acceleration.
- Area under graph = distance (or displacement) covered.
Equations of Motion (for uniform acceleration)
- v = u + at (final velocity)
- s = ut + ½ at² (distance)
- v² = u² + 2as (velocity-displacement relation)
- u: initial velocity, v: final velocity, a: acceleration, t: time, s: displacement.
Uniform Circular Motion
- Uniform circular motion: object moves at constant speed along a circular path.
- Only the direction of velocity changes, so acceleration is present.
- Speed in a circle: v = 2πr / t, where r is radius, t is time for one rotation.
Key Terms & Definitions
- Reference Point (Origin) — Chosen fixed position to describe motion.
- Distance — Total length of path covered by an object.
- Displacement — Shortest distance from initial to final position (with direction).
- Speed — Rate of covering distance (no direction).
- Velocity — Speed in a specified direction.
- Acceleration — Rate of change of velocity per unit time.
- Uniform Motion — Constant speed and direction.
- Non-uniform Motion — Changing speed and/or direction.
- Uniform Circular Motion — Movement in a circle at constant speed.
Action Items / Next Steps
- Complete textbook exercises at the chapter’s end.
- Practice plotting and interpreting distance-time and velocity-time graphs.
- Memorize and apply the equations of motion for problem solving.
- Perform suggested activities to deepen understanding of concepts.