Which quantity is defined as the speed of an object in a particular direction?

• A. The speed of an object in a particular direction.
• B. The force applied to a unit area of surface.
• C. The capacity to do work.
• D. The degrees of something in Celsius or Fahrenheit.

Answer: (A)

Velocity is the quantity that describes how fast something is moving in a specific direction. It combines speed with direction, making it a vector. For example, a car moving at 20 meters per second toward the north has a velocity of 20 m/s north. Speed alone only tells how fast something is moving and lacks direction, so it doesn’t fully describe the motion. The other terms refer to different concepts: pressure (force per area), energy (capacity to do work), and temperature (how hot or cold something is). So the description given matches velocity.