posted by Steph on .
A driver of a car going 90.0km/h suddenly sees the lights of a barrier 40.0 metres ahead. It takes the driver 0.75 seconds before she applies the brakes, and the average acceleration during braking is -10.0 m/s squared. Does the car hit the barrier?SHow all your work. (2 parts)
V = 90km/h = 90km/h / 3600s/h = 0.025km/s = 25m/s.
d = 25m/s * 0.75s = 18.75m = Distance
traveled before brakes are applied.
d = 40 - 18.75 = 21.25m = max stopping
Vf^2 = Vo^2 + 2ad = 0,
(25)^2 + 2(-10)d = 0,
625 - -20d = 0,
-20d = -625,
d = -625 / -20 = 31.25m = Distance traveled after brakes are applied.
The car will hit the barrier, because it was required to stop within 21.25m
after the brakes are applied.