A 1000 kg automobile is at rest at a traffic signal. At the instant the light turns green, the automobile starts to move with a constant acceleration of 4.0m/s2. At the same instant a 2000 kg truck, traveling at a constant speed of 8.0 m/s, overtakes and passes the automobile.
(a) How far is the com of the automobile-truck system from the traffic light at t = 3.0 s?
(b) What is the speed of the com then?