1. The problem statement, all variables and given/known data An object 20 cm. to the left of a converging lens with focal point 0.3 cm is moved to the left at a constant 5 cm/s. How fast is the image moving? 2. Relevant equations v = vo + at 1/f = 1/u + 1/v 3. The attempt at a solution Since there is no acceleration, I got 5 m/s as the velocity but I don't know how to treat a non-constant value of u. The units don't match up in the lens equation, so what should I do?