1. A body of mass 5 kg accelerates from 12 m/s to 20 m/s in 4 seconds due to the application of a force on it. Calculate the magnitude of this force (in N).
9. Find the power of a convex lens if the image formed is at a distance of 25 cm from the lens when the object is placed on the other side of the lens at 12 cm from the optical centre?