Given that the mass of the car is m = 2000 kg and initial speed u = 20 m/s.
Here, three values of time are given.
(a) t1 = 10 s
(b) t2 = 4 s
(c) t3 = 1.2 s
In all three cases, the final velocity vis zero.
Impulse = change in momentum
= mv-mu
![\begin{gathered} \operatorname{Im}\text{pulse = 2000}*0-2000*20 \\ =-40000\text{ Kg m/s} \end{gathered}]()
If the time duration is increased then force will be decreased as
![\operatorname{Im}\text{pulse = force}* time]()
Force will be lowest for 10s and greatest for 1.2 s.
The impulse will be the same for all three cases as the change in momentum is the same.