physics
posted by Alex .
A car and a motorcycle start from rest at the same time on a straight section of the road. However, the motorcycle starts 29.6 m behind the car. The car accelerates at a uniform rate of 3.9 m/s^2 while the motorcycle accelerates at a constant rate of 4.2 m/s^2. How much time elapses until the motorcycle overtakes the car?

They travel the same time, and 29.6m different in distance.
dm=1/2 am t^2
dc=1/2 ac t^2
subtract the second equation from the first
dmdc=1/2 (amac)t^2
29.6=1/2 (amac)t^2
solve for t. 
A car traveling at +7.8 m/s accelerates at the
rate of 0.65 m/s
2
for an interval of 1.6 s.
Find vf .
Answer in units of m/s 
14.04