18 km/hr1000m/km1 hr/3600 sec= 5 m/sec
85 km/hr= 23.6 m/s
distance = 4000m
distance= initial distance+initial velocitytime+ 1/2 accelerationtime^2
initial distance=0
4000= 5.0t+ 1/2 (accel)(time)^2
Velocity=initial velocity+ acceleration time
23.6 m/s= 5.0 m/s+ acceleration * time
We now have two equations and two unknowns. Solve them and you have your answer.
