Momentum (p) is equal to the product of an object's mass (m) and its change in velocity (v).
Change in velocity (v) results in change in momentum (p), which is equal to impulse. Impulse (J) is also equal to an applied force (F) over a period of time (t).
Combining p=mv and J=F t together:
m (v final - v initial) = F t
(2,500 kg) (70 m/s - 30 m/s) = F (10 s)
Solving for F we get:
10,000 N of force