Further calculate the tangential (orbital) velocits or Moon

It is due to its inertial movementum established during its creation,but simultaneously being nearer to earth could feel the gravitational force acting in a perpendicular direction to its velocity could match to centripetal force in pulling it to move around the earth. So that velocity could now be termed as tangential velocity being tangent to moon's present path of motion.

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length