Circular Motion (HT only)
- Velocity is a vector quantity, and the velocity of an object is its speed in a given direction
- When an object travels along a circular path, its velocity is always changing
- The speed of the object moving in a circle might be constant - that is, it is travelling the same distance every second
- However, the direction of travel is always changing as the object moves along the circular path
- This means that an object moving in circular motion travels at a constant speed but has a changing velocity
- The image below shows an example of a famous object that moves in a circular path with a constant speed but changing direction:
The International Space Station’s velocity is always changing - it whizzes around the Earth at a constant speed of about 7660 m/s but is always changing direction
Examiner Tip
You may be asked to explain why motion in a circle involves constant speed but changing velocity, so remember to mention that velocity is a vector quantity, so both magnitude and direction are important.
Even though the magnitude (speed) doesn’t change, its direction does - so the velocity itself is changing. Because of this, objects in circular motion are always accelerating!
