Ask a Teacher

Search



Two cars are adjacent to each other on a four lane highway. The first car accelerates uniformly from rest at 3.0 m/s2 the moment the light changes to green. The second car approached the intersection already moving at 18 m/s and is beside the first car at the instant the light changes. It then continues driving with a constant velocity. Determine the following . When are the two cars side by side again? When do they have the same velocity?

1st car
u=0
a=3m/s^2
v=3t where t is the time
S=(1/2)at^2
  =(1/2)*3t^2
2nd car
u=18m/s
a=0
v=18m/s^2
S=18t
The cars have the same velocity when 3t=18
t=18/3
            =6s.
They are side by side when distance travelled is the same.
ie, 18t=(1/2)*3t^2
     18=(1/2)*3t
       t=(18*2)/3
        =12s.


comments powered by Disqus