Posted by **christina** on Thursday, January 16, 2014 at 9:17pm.

A car traveling at the speed of 30.0 m/sec encounters an emergency and comes to a complete stop. how much time will it take for the car to stop if its rate of deceleration is -4.0 m/sec

- science/math -
**Reiny**, Thursday, January 16, 2014 at 11:25pm
Using Calculus

a = -4

v = -4t + c

when t=0 , v = 30

30 = 0 + c

v = -4t + 30

s = -2t^2 + 30t + k

when t = 0 , s = 0, so k = 0

s = -2t^2 + 30t

when the car stops, v = 0

4t = 30

t = 30/4 = 7.5 seconds

when t = 7.5

s = -2(7.5)^2 + 30(7.5) = 112.5 m

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