A car is travelling 15 m/s when the drives a child standing on the road .she takes 0.8 seconds to react the steps on the brakes and slows at 5.0m/s .how far does the car go before it stops?
drifts at constant speed for 15 m/s * 0.8 s = 12 m
You mean a = - 5.0 m/s^2 I suspect, not 5.0 m/s
a = -5.0
v = Vi + a t = 15 - 5 t
v = 0 at stop
5 t = 15
t = 3 seconds to stop with brakes on
average speed during braking = 15/2 = 7.5 m/s
distance braking = 7.5 m/s * 3 s = 22.5 meters braking
total distance = 12 + 22.5 = 34.5 meters ! Yikes !!! a third of a football field