A constant net force perpendicular to the velocity of an object causes it to travel in a circular path. Such a force can be described as a centripetal force.
For an object moving at a constant speed in a circle:
Centripetal acceleration is given by: 
and 
= yields: = 2 and 
Circular motion can be investigated with whirling bungs: a bung is swung in a horizontal circle. A suspended weight remains stationary if the force it provides (i.e. its weight) is equal to the centripetal force required to make the bung travel in a circular path. By varying the weight and the angular velocity etc., properties of circular motion can be investigated. A glass tube is used (low friction) with a paperclip to ensure that the radius does not change.