In physics, how does velocity differ from speed?

• A. Velocity and speed are always identical because both measure distance divided by time.
• B. Speed includes direction of motion, while velocity does not.
• C. Velocity is a scalar quantity, while speed is a vector quantity.
• D. Velocity is a vector quantity (magnitude and direction), while speed is a scalar quantity (magnitude only).

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the definitions of speed and velocity. Speed is the rate at which an object covers distance, and it is a scalar quantity, meaning it has only magnitude and no direction.
2. Step 2: Recognize that velocity is the rate of change of displacement, which means it includes both magnitude and direction, making it a vector quantity.
3. Step 3: Note that speed is calculated as the total distance traveled divided by the time taken, expressed as \(\text{speed} = \frac{\text{distance}}{\text{time}}\).
4. Step 4: Understand that velocity is calculated as displacement divided by time, expressed as \(\text{velocity} = \frac{\text{displacement}}{\text{time}}\), where displacement is a vector quantity.
5. Step 5: Conclude that the key difference is that velocity includes direction (vector), while speed does not (scalar), which affects how each quantity describes motion.