Introduction to Physics Concepts
In this lecture, we cover basic physics concepts such as displacement, velocity, acceleration, projectile motion, Newton's laws, and forces.
Distance vs. Displacement
- Distance: Scalar quantity; total path traveled, without regard to direction.
- Displacement: Vector quantity; difference between the initial and final position; requires direction.
- Example: John walks 8m east, then 3m west.
- Distance = 11m (8 + 3)
- Displacement = 5m (final position - initial position)
- Positive displacement: East/North
- Negative displacement: West/South
Speed and Velocity
- Speed: Scalar quantity; how fast an object is moving; always positive.
- Example: Car at 30 m/s travels 30 meters every second.
- Formula:
D = v * t
- Velocity: Vector quantity; speed with direction; can be positive or negative.
- Example: Train moving at 30 m/s west: velocity = 30 m/s west.
- Formula:
v = D / t for average speed; same formula for average velocity but using displacement.
Acceleration
- Describes how fast velocity changes; vector quantity.
- Example: Sports car increases speed faster than a truck (greater acceleration).
- Formula:
a = (Vf - Vi) / t
Motion Analysis
- Positive Acceleration: Speed increases.
- Negative Acceleration: Speed decreases (object slows down).
- Projectile Motion: Objects under gravity; no friction assumed.
- 1D motion: Only Y-direction considered.
- 2D motion: Both X and Y directions; example: ball kicked off a cliff.
Newton's Three Laws
- First Law: Object at rest stays at rest; object in motion stays in motion unless acted upon by a force.
- Second Law:
F = ma (Force equals mass times acceleration).
- Example: 10kg mass with force of 80N has an acceleration of 8 m/s².
- Third Law: For every action, there is an equal and opposite reaction.