Explanation:
Formula for distance travelled:
x= ut + 1/2at^2
x is 1.4km, convert this to m since acceleration is in m, = 1400m
u is initial velocity, in this case assume 0
a is acceleration, = 4m/s^2
t is unkown and what we want to find out
Substitute value into formula,
1400 = 0t + 1/2(4)t^2
1400 = 2t^2
t^2 = 1400/2
t^2 = 700
t = 26.458s
Formula for acceleration:
a = (v-u)/t
at= v-u
Substitute value,
4(26.458) = v - 0
v = 105.832 m/s