i. If a rock is thrown upwards with a. velocity of 20 metres per second, its height, in metres, is given by HOE] = 4.9t2 + 20:. [Calculus method and not physics methods must be used) (3) Find the velocity at any time 1% seconds. (b) After how many seconds will the rock stop rising and begin to fall? (C) After what time, and with what velocity will the rock hit the ground