Let us write the following equations:

Vf = Vi + a t (1)

D = Vi t + 1/2 a t ^2 (2)

Since Vi = 0 we can rewrite (1) and (2) as follows

Vf = a t (1)

D = 1/2 a t^2 (2)

Then,

D = 1/2 x Vf x t Therefore 100 m = 1/2 x 180000/3600 x t It yields t = 4 seconds

By replacing 4 seconds in equation (1)

a = (180000/3600) / 4 = 12,5 m/sec^2

Finally, F = m x a

F = 3000 Kgs x 12,5 m/sec^2 = 37500 Newtons