Acceleration

An object is accelerating if its velocity is changing. Remember: velocity is a vector quantity, which has both a magnitude (speed) and a direction (the direction it is moving).

So, an object is accelerating if either its SPEED is changing or if the DIRECTION the object is moving in changes. Or both!

For example, if an object is moving in a straight line but its speed is changing, this object is accelerating (or its acceleration is not equal to zero). For example, the car below is accelerating. Its speed increases with each second. (You can tell because it moves farther and farther with each second.)

If an object is moving at the same speed but changing directions, the object is accelerating. For example, the car below is moving on a circular track at a constant speed (moving the same distance every 10 seconds). But it is constantly changing directions. Because it is changing directions, it is accelerating (or its acceleration is not equal to zero).

If an object is changing in speed and direction, it is accelerating. In the example below, the speed of the car is increasing from 0 seconds to 30 seconds. The car is also (constantly) changing its direction. So, this car is accelerating--and its acceleration is greater than the acceleration of the car above that changes direction without changing speed.

Go to the next page to play the Acceleration Game...