---

Brock University Physics courses Physics Department

By: E.Sternin

---

Position, velocity, and acceleration
in uniform circular motion

If you see this text, your browser is not Java-capable.
Enable if you can, and Reload/Refresh this page.

As you start the motion, notice how vector v remains perpendicular to vector r, at all times. This is because the magnitude of r remains constant, and only its direction changes. Thus the vector dr which describes the change in r ends up tangential to the circular trajectory (the r-circle) in the limit of small angular increments.

The situation repeats itself for vector a which at all times remains perpendicular to the vector v (and along dv, in the limit of small angular increments).

As a result, the vector a is always in the direction opposite to that of the vector r, i.e. is directed toward the center of the circle; hence this acceleration is called centripetal.