A 1550kg car, traveling with a velocity of 12m/s plows into a 1220kg stationary car. During the collision the two cars lock bumpers and then move together as a unit. (a) what is tehir common velocity just after the impact? (b) What fraction of the initial kinetic energy remains after the collision. (a) Pf=Pi (m1+m2)vf=m1vi1 (1550kg+1220kg)vf=1550kg(12m/s) 2770kgvf=18600kg m/s vf=6.71 m/s I know my answer for part A is correct but part B i really have no idea how to approach it.