In order to cause a body to move along a circular path we must apply

for a body to move on a circular path with constant speed the force applied on it should be such that it changes the direction of velocity but not its magnitude, this is possible only if the force acts perpendicular to the direction of velocity at each and every point of its motion, since velocity is along the tangent, this force must be along the radius and towards the canter, this force is centripetal force