~(c)(i) The second stone moves upwards and its acceleration g = 10m/s\(^2\). From equation v = u - gt
10 = 20 - 10t -10 = -10t
t = 1
The second stone has been in air for 1s before they met.
(ii) The first stone has been moving for (1 + 2)s = 3s
From equation v = u + gt
= 2 - (10 x 3) = 20 - 30 = -10m/s
The minus sign means the first stone is moving down and its velocity is 10m/s.

