<p>For #18b, to calculate the impuse exerted on the fullback, I used the formula delta(P)=F*delta(t). I know that delta t = 0.75s as given in the problem. But to find delta(P) which is the impulse, I need F. How can I found the force?</p>
<p>You know the acceleration a = (delta v)/(delta time) = (0 - 4)/0.75, and you know the fullback's mass. Compute F = ma .</p>