LINEAR MOTION IN A STRAIGHT LINE: SPEED AND VELOCITY
Understanding Basic Concepts and Real-World Applications
Presented by: Ma. Johanna B. Testa
LINEAR MOTION: SPEED AND VELOCITY
INTRODUCTION TO LINEAR MOTION
Definition:
- Linear motion is movement along a straight line.
- Also known as rectilinear motion.
Types:
• Uniform Motion: Constant speed
• Non-uniform Motion: Changing speed or direction
DISTANCE VS. DISPLACEMENT
Distance:
• Total path covered
• Scalar quantity
Displacement:
• Straight-line change in position
• Vector quantity
Example:
100 m lap around a track: Distance = 100 m, Displacement = 0 m (if return to start)
WHAT IS SPEED?
Definition:
How fast an object is moving (no direction).
Formula:
Speed = Distance / Time
Unit:
m/s or km/h
Example:
120 km in 2 hours → Speed = 60 km/h
WHAT IS VELOCITY?
Definition:
Rate of change of displacement, includes direction.
Formula:
Velocity = Displacement / Time
Unit:
m/s, with direction
Example:
300 m east in 15 s → Velocity = 20 m/s east
SPEED VS. VELOCITY
Speed:
• Scalar
• No direction
• Always positive
Velocity:
• Vector
• Has direction
• Can be negative
Example:
Speed: 60 km/h
Velocity: 60 km/h north
UNIFORM VS. NON-UNIFORM VELOCITY
Uniform Velocity:
• No change in speed or direction
• Example: Cruise control on highway
Non-uniform Velocity:
• Change in speed or direction
• Example: Car turning or accelerating
GRAPHING LINEAR MOTION
Distance-Time Graph:
• Straight line = constant speed
Displacement-Time Graph:
• Positive slope = forward
• Negative slope = return
Velocity-Time Graph:
• Flat line = constant velocity
SAMPLE PROBLEM
Problem:
Bus travels 180 km north in 3h, then 60 km south in 1h.
a) Distance = 240 km
b) Displacement = 120 km north
c) Avg speed = 60 km/h
d) Avg velocity = 30 km/h north
REAL-LIFE APPLICATIONS
• GPS Navigation: ETA (Estimated Time of Arrival), speed tracking
• Sports: Runner velocity analysis
• Space: Rocket speeds (NASA)
• Road Safety: Radar speed checks
• Robotics: Movement algorithms
CLASSROOM ACTIVITY IDEA
Speed Lab:
Use stopwatch + meter stick to time a 5m walk/run.
Calculate speed & velocity.
Extension:
Return walk shows displacement = 0.
Plot on distance-time graph.
SOURCES & REFERENCES:
• Khan Academy – One-Dimensional Motion
• McGraw-Hill Education – Physics Textbook
• NASA – Trajectory Concepts
• Physics Classroom – Kinematics
• Oxford Academic Journals – Physics Education