s = (v-u)/2 * t, where v is the final velocity, u is the initial velocity, s is the displacement and t is the time.
40 = (v-2.8)/2 * 8.5
4.71 = v-2.8/2
9.41 = v- 2.8
v = 12.2 m/s
v^2 = u ^2 +2as where v is the final velocity, u is the initial velocity, a is the acceleration and s is the displacement.
12.2^2 = 2.8^2 + 2a(40)
80a = 12.2^2 - 2.8^2
80a = 148.84 - 7.84
80a = 141
a = 1.7625m/s^2