A car accelerates from rest at 7.9 m/s2.

Question

How much time does it need to attain a
speed of 5 m/s?

Answer 1

a = (Vf - Vo) / t = 7.9 m/s^2,
(5 - 0) / t = 7.9,
5/t = 7.9,
t = 5 / 7.9 = 0.63 s.