26. Speed, Velocity, Distance & Displacement

1. Scalar vs. Vector Quantities

Understanding the difference between these two types of quantities is essential for physics:

• Scalar Quantities: Only have magnitude (size).

  • Speed: How fast an object is moving (e.g., 4 m/s).

  • Distance: How much ground an object has covered (e.g., 10 m).

• Vector Quantities: Have both magnitude and direction.

  • Velocity: Speed in a specific direction (e.g., 6 m/s East).

  • Displacement: Distance in a specific direction (e.g., 40 m East).

2. Calculating Speed and Velocity

Speed Formula (Scalar)

$\text{Speed} = \frac{\text{Distance}}{\text{Time}}$

Velocity Formula (Vector)

$\text{Velocity} = \frac{\text{Displacement}}{\text{Time}}$

• Negative Velocity: In calculations, a negative velocity is often used to represent an object moving in the opposite direction (e.g., backwards).

• Average Speed: If an object does not move at a constant rate, divide the total distance by the total time to find the average speed.

3. Typical Speeds to Remember

The exam often expects you to have an idea of typical real-world speeds: