At the instant the traffic light turns green, an automobile starts with a constant acceleration a of 2.3 m/s2. At the same instant a truck, traveling with a constant speed of 9.4 m/s, overtakes and passes the automobile.

Question

At the instant the traffic light turns green, an automobile starts with a constant acceleration a of 2.3 m/s2. At the same instant a truck, traveling with a constant speed of 9.4 m/s, overtakes and passes the automobile. 
(a) How far beyond the traffic signal will the automobile overtake the truck? 
 m
(b) How fast will the car be traveling at that instant?
 m/s

bobpursley · Answer

at some time t, the same time for both cars, they have went the same distance d. You have two equations Truck: d=vi*t Car: d=1/2 a t^2 set the equal, solve for t, thensolve for d.