Posted by **Steph** on Sunday, February 13, 2011 at 4:58pm.

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)

- Physics -
**Henry**, Tuesday, February 15, 2011 at 5:47pm
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

dist.

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.

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