define deceleration
When you brake to stop your car, you are decelerating. When a ball rolls on the ground and slows down to a stop, the ball is decelerating. Deceleration is the term used for acceleration that causes an object to slow down, while acceleration is motion where the speed of an object changes every second. However, in everyday usage, acceleration is usually taken to mean speeding up. Now that you know what deceleration is, let's look at an example.