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Home Q & A Board Science-Related Homework Help Physics
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smartgirl777 smartgirl777
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11 years ago
A car is traveling at 30 m/s. The driver sees a child and, with a 0.80 second reaction time, stops the car with a deceleration of -8m/s^2. How long does it take for the car to come to a complete stop and how far does it travel during the entire stop?
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IlluminatusIlluminatus
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11 years ago
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#2
11 years ago
during the reaction time the car will travel
0.8(30) = 24 m

the time of deceleration is
v = at
t = v/a
t = 30 /8
t = 3.75 s

the distance traveled during braking is the average velocity times time
3.75(30 + 0)/2 = 56.25 m

so the total elapsed time is
3.75 + 0.8 = 4.55 s

and the total distance traveled is
56.25 + 24 = 80.25 m
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