Measurement of Speed

Key Notes :

1. Definition of Speed

  • Speed is the distance traveled per unit of time.
  • It is a scalar quantity, meaning it only has magnitude (no direction).
  • The formula for speed is
  • Where:
    • Distance is the total path length traveled by an object (measured in meters, kilometers, etc.).
    • Time is the duration taken to cover the distance (measured in seconds, minutes, hours, etc.).

2. Units of Speed

  • The SI (International System) unit for speed is meters per second (m/s).
  • Other common units include kilometers per hour (km/h), miles per hour (mph), etc.

3. Calculating Speed

  • To calculate speed, divide the total distance by the total time taken.
    • Example: If a car travels 100 kilometers in 2 hours, the speed is:

4. Types of Speed

  • Uniform Speed: When an object covers equal distances in equal intervals of time.
    • Example: A train moving at a constant speed of 60 km/h.
  • Non-uniform Speed: When an object covers unequal distances in equal intervals of time.
    • Example: A car moving at varying speeds.

5. Average Speed

  • Average speed is the total distance traveled divided by the total time taken.
  • It is used when the speed is not constant over the entire journey.

6. Instantaneous Speed

  • Instantaneous speed is the speed of an object at a particular moment in time.
  • It can be measured using devices like a speedometer.

7. Speed-Time Graph

  • A graph that shows how speed changes with respect to time.
  • The slope of the graph represents acceleration.
  • A flat line indicates uniform speed, while a sloping line indicates a change in speed (acceleration or deceleration).

8. Relationship Between Speed, Distance, and Time

  • You can rearrange the formula to calculate distance or time if speed is known:
    • Distance = Speed × Time
    • Time = Distance ÷ Speed

9. Factors Affecting Speed

  • Friction: Can slow down moving objects, decreasing their speed.
  • Air resistance: Can also reduce speed, especially for objects moving at high speeds, like cars or planes.
  • Terrain: Slopes and rough surfaces can decrease speed.

10. Examples in Real Life

  • A cyclist riding at a steady 10 km/h.
  • A plane traveling at 800 km/h.
  • A person running at 6 m/s.

11. Applications of Speed

  • Understanding speed helps in various fields like sports, transportation, and vehicle safety.
  • It’s important for calculating travel time, analyzing motion in physics, and managing traffic speeds.

Let’s practice!