an object 40 cm from a converging lens of focal length 20 cm moves the velocity of 5 cm per second towards the less calculate the image position after 2 seconds?

Answer 1

1/do + 1/di=1/f
first, calculate the di original (you have do, f)
Then, calcualte the do after 2 seconds (do final=40 -5(2) ) then calculate the final di (original lens equation, you have the new do, f.
That is the position of the image after 2 seconds

Answer 2

I don't understand