How much impulse is required to change the velocity of a 2500 kg truck
by 15 m/s?

before we can answer, we have to see the choices that are printed there with the question.   that's the only way we can point you to the correct one.

96.77 amp

explanation:

rl = 250/100 = 2.5 ohms.

egl = 250 + (100 × 0.1) + 2 = 262 v.

at 700 r.p.m., eg2 = 262 × 700/1000 = 183.4 v.

if ia is the new current, then eg2 - 2 - (ia × 0.1) = 2.5 ia

which means this will give ia = 96.77 amp.