An object is changing its velocity anytime its speed or direction is changing. This change in velocity is known as acceleration.
Understanding Velocity and Acceleration
Velocity is a vector quantity, meaning it has both magnitude (speed) and direction. Therefore, velocity changes in two main ways:
- Change in Speed: The object speeds up (positive acceleration) or slows down (negative acceleration, also known as deceleration).
- Change in Direction: Even if the object maintains a constant speed, a change in direction signifies a change in velocity and therefore acceleration.
Examples of Changing Velocity
Here are some examples to illustrate when an object's velocity is changing:
- A car accelerating from a stop: The car's speed is increasing, thus its velocity is changing.
- A car braking to a stop: The car's speed is decreasing, thus its velocity is changing.
- A car turning a corner at a constant speed: While the speed remains constant, the direction of the car is changing, so its velocity is changing.
- A ball thrown upwards: As the ball rises, gravity slows it down (negative acceleration), and as it falls, gravity speeds it up (positive acceleration). In both cases, the velocity is changing.
- An object moving in a circle at a constant speed: Although the speed is constant, the object is constantly changing direction, which means its velocity is constantly changing. This is called centripetal acceleration.
Acceleration Explained
Acceleration is the rate at which velocity changes over time. Mathematically, it's represented as:
Acceleration = (Change in Velocity) / (Change in Time)
A non-zero acceleration always indicates a change in velocity, whether it's a change in speed, direction, or both.
In summary, an object is changing its velocity (i.e., accelerating) whenever its speed, its direction, or both are changing.
