Question

Use Formula = Change in momentum =mv-mu;
u=0
F =mv - mu / t

Answer 1

change in momentum=mv-mu
54km/h=15m/s=u
v=0m/s
m=2000kg. mv-mu=m(v-u)=2000(0-15)=2000×-15=-30000kgm/s
negative sign indicates that momentum changed in the direction opposite to the motion
retardation=v-u/t=0-15/15=-1m/s×s is negative acceleration