What is the acceleration of an object that has a velocity of 18 m/s and is moving in a circle of radius 30m?

Acceleration = V^2/r = 18^2 / 30 = 10.8 m/s^2

Well, first of all, 18 m/s is the object's speed, but not its velocity.

Velocity consists of the object's speed AND direction, and this

particular object's direction is constantly changing, since it's

moving around a circle. So its velocity is constantly changing too.

Centripetal acceleration = (speed) ² / (radius)

= (18 m/s) ² / (30 m)

= (324 m²/s²) / (30 m)

= 10.8 m/s²

(about 1.1 G)