A rock of mass 2kg is released from rest at the top of a vertical cliff 80m high. At the same instant, a ball of mass 0.5kg is projected upward from the foot of the cliff with a speed of 40ms−1. Neglect air resistance and take g=9.8ms−2. Take the downward direction as positive.
(i) Write the equations of motion for the rock and for the ball.
(ii) Calculate the time after which the two objects cross each other.
(iii) Determine the distance of the meeting point from the top of the cliff.
(iv) Would any of the numerical answers change if the masses of the two objects were interchanged? Give a physical reason for your answer.