Introduction to Basic Physics Concepts
This lecture covers fundamental physics concepts like:
- Distance and Displacement
- Speed and Velocity
- Acceleration
- Projectile Motion
- Newton's Three Laws
- Forces and Momentum
Distance vs. Displacement
- Distance: The total length traveled regardless of direction.
- Example: Distance from one city to another (e.g., 100 miles).
- Displacement: The shortest distance from the initial to the final position, including direction.
- Example:
- John walks 8 m east and then 3 m west.
- Total distance = 11 m (8 + 3).
- Displacement = 5 m (final position 5 m from initial position 0 m).
- Key Points:
- Distance is a scalar quantity (only magnitude).
- Displacement is a vector quantity (magnitude + direction).
Speed and Velocity
- Speed: A measure of how fast something is moving (scalar).
- Example: A car traveling at 30 m/s.
- Velocity: Speed with direction (vector).
- Example: A train moving at 45 m/s (speed) vs. 30 m/s west (velocity).
- Key Equations:
- Speed = Distance / Time
- Velocity = Displacement / Time
Average Speed vs. Average Velocity
- Average Speed: Total distance traveled divided by total time.
- Average Velocity: Total displacement divided by total time.
Acceleration
- Acceleration: The rate of change of velocity over time.
- Formula: a = (final velocity - initial velocity) / time.
- Positive acceleration indicates an increase in velocity; negative indicates a decrease.
- Example:
- A truck accelerates from 0 to 60 mph in 30 seconds: a = 2 mph/s.
- A sports car accelerates from 0 to 60 mph in 5 seconds: a = 12 mph/s.
Gravitational Acceleration
- On Earth: g = -9.8 m/sĀ² (causes objects to fall).
- Affects vertical velocity but not horizontal velocity in projectile motion.
Projectile Motion
- A projectile moves under the influence of gravity; its path is called the trajectory.
- In one-dimensional motion, gravity acts vertically.
- In two-dimensional projectile motion, horizontal (vx) remains constant, while vertical (vy) changes due to gravity.
Newton's Laws of Motion
First Law
- An object at rest remains at rest, and an object in motion continues in motion unless acted upon by a net force.
Second Law
- F_net = m * a (where F_net is the net force, m is mass, and a is acceleration).
- Example: A 10 kg mass experiences an 80 N force:
- a = F/m = 80 N / 10 kg = 8 m/sĀ².
Third Law
- For every action, there is an equal and opposite reaction.
Conclusion
These fundamental concepts lay the groundwork for understanding how objects move, interact, and respond to forces in the physical world.