9.7 Circular motion
Newton’s first law (inertia) tells us that an object’s velocity will only change if the object is acted upon by some force. Velocity is a vector—both magnitude and direction are important. Therefore, your velocity can be changing, even if your speed is constant.
Objects traveling around a circular path do experience an acceleration, called centripetal (“center-seeking”) acceleration. Moving at a speed v around a path of radius r, an object’s acceleration is
ac = v 2⁄r
There is no single force called “the centripetal (or centrifugal) force” Circular motion is an effect of the net force—the total of all forces—acting on an object.