Question
A car leaves skid marks 90 long on the highway in coming to a stop.
Assuming a deceleration of 3.5m/s^2, estimate the speed of the car just before braking.
Assuming a deceleration of 3.5m/s^2, estimate the speed of the car just before braking.
Answers
Damon
0 = Vi - a t
so
t = Vi/3.5
d = Vi t - (1/2)(3.5) t^2
90 = Vi^2/3.5 - 1.75 Vi^2/12.25
Vi^2 - .5 Vi - 315 = 0
Vi = [ .5 +/- sqrt ( .25 + 1260) ]/2
Vi = [ .5 +/- 35.5 ] / 2
Vi = 18 m/s
so
t = Vi/3.5
d = Vi t - (1/2)(3.5) t^2
90 = Vi^2/3.5 - 1.75 Vi^2/12.25
Vi^2 - .5 Vi - 315 = 0
Vi = [ .5 +/- sqrt ( .25 + 1260) ]/2
Vi = [ .5 +/- 35.5 ] / 2
Vi = 18 m/s
Anonymous
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