a particle falling under gravity falls 39m in certain second find time required to cover the next 30 m take g=9.8

Answer 1

V^2 = Vo^2 + 2g*d.
V^2 = 0 + 19.6*39 = 764.4
V = 27.65 m/s.

d = Vo*t + 0.5g*t^2 = 30 m.
27.65t + 4.9t^2 = 30
4.9t^2 + 27.65t - 30 = 0
Use Quadratic Formula and get:
Tf = 0.931 s. = Fall time.