Since, a= g = 9.8 m/s2

Therefore,

v = u + at

4g ms^-1 = 0 + 9.8 x 1

4g ms^-1 = 9.8 ms^-1

Average velocity = - 1/2gt= 1/2 * 9.8 * 1.0 s

= 4.9 m/s