A convex lens of power 3 D is held in contact with a concave lens of power -1 D. A parallel beam of light is made to fall on the combination. At what distance from the
combination will the beam get focused?

Alarge cruise ship of mass 7.00 ✕ 107 kg has a speed of 11.6 m/s at some instant. (a) what is the ship's kinetic energy at this time? (b) how much work is required to stop it? (give the work done on the ship. include the sign of the value in your answer.) (c) what is the magnitude of the constant force required to stop it as it undergoes a displacement of 3.00 km?