Why is something accelerating when it is traveling in a circle?

Answer 1

Something is accelerating when it is traveling in a circle because the direction of its velocity is changing.

It is important to understand that a velocity not only has a magnitude but it also has a direction. In general, if the magnitude and/or direction of an object's velocity is changing, we say that it is accelerating.

Again, if something is traveling and only the direction that it is traveling changes, we still say it is accelerating because the direction that it is traveling is changing.

This is the case when something is traveling in a circle at constant speed. If you where to represent its velocity by a vector you would find that while the magnitude of the vector does not change over time, the direction of the vector does. In fact, over a very short period of time, if you where to represent the change in direction of its velocity by a vector, you would find that that "difference vector" points directly toward the center of the circle.

Again, this is all a bit confusing because when we generally use the word "accelerate" we mean that something is speeding up. However one just has to get use to the idea that when something is accelerating, it may be that only the direction of its velocity is changing and not necessarily the magnitude of its velocity.

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Answer 2

Yes. Most people think of acceleration as a change in speed, but it's actually a change in velocity, which is a combination of speed and direction. Since the direction of motion is always changing if an object is moving in a circle, then the object must continually accelerate to maintain the circular motion.