A motorcycle has initial velocity of 5 m/s. After 3 seconds, the velocity is 7 m/s. The displacement of the motorcycle in 3 seconds is :

Using the equation of motion s = ((u+v)/2) × t, where u = 5 m/s (initial velocity), v = 7 m/s (final velocity), and t = 3 s. Therefore, s = ((5+7)/2) × 3 = (12/2) × 3 = 6 × 3 = 18 m. The motorcycle undergoes uniform acceleration during this interval, so this average-velocity formula correctly gives the displacement as 18 metres.