(1.2 ) Use the following kinematic equation to derive an equation that tells you i) how long the ball is in the air At if it left the ground with a speed v straight up , and returned to the ground with same speed v , and ii) the initial speed of the ball if it was in the air for a time At : Ay v At + last2, (2 marks ). Helpful hints : Remember , we have defined the ground as y = 0 m. Assume up is positive so that the acceleration due to gravity is - g. Furthermore , for i) your answer should have At on the left-hand side of the equation and other variables on the right , for ii) your answer should have v on the left -hand side of the equation and the other variables on the right