Explain what is meant by positive acceleration and negative acceleration (retardation). Give one example for each.

Positive acceleration occurs when the velocity of an object increases in the direction of motion. For example, a car speeding up from a traffic light. Negative acceleration, also known as retardation or deceleration, occurs when the velocity of an object decreases, or its speed reduces, in the direction of motion. For example, a car applying brakes to slow down.