Untitled

           Tangential Velocity (v_t)
           ----------------------->
           |                     
           |  
           |             O  (Center of the circle)
           |            /|\
           |          /   |
           |       r     |
           |          \   |
           |           \|
           |         Tangent to the circle
           |
           --------------------> Radial direction (r)