# physics

a motorist traveling at 18m/s approaches traffic lights. when he is 30m from the stop line they turn red .it takes 0.7s before he can react by appling the breakes. the car slow down at a rate of 4.6m/s^2 how far from the stop line will he come to rest and on which side of it?

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1. distance traveled: .7*18+distance braking
distance trveled= .7*18+35.2m

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2. nice but it is not cear

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3. A distance travelled before applying a brake =0.7*18=12.6m
A distance travelled after applying brakes=vi2/2a,where as vf=0,s=sqrt18/2*4.6=35.2m
The total the motorist travel=12.6+35.2=47.8m
Therefore the distance between the stop line and the motorist stopped (the total motorist traveled) =47.8m-30m=17.8m

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