Problem 2.46 The minimum stopping distance for a car traveling at a speed of 30

Question

Problem 2.46

The minimum stopping distance for a car traveling at a speed of 30 m/s is 60 m, including the distance traveled during the driver's reaction time of 0.47s

What is the minimum stopping distance for the same car traveling at a speed of 45m/s ?

Express your answer to two significant figures and include the appropriate units.

Here is my work, mastering physics is telling me that there is a rounding error or I am using the wrong significant figures... please help where I am going wrong!!

Explanation / Answer

case 1:-

distance travelled in 0.47s = 30*0.47 = 14.1m

so distance travelled while retarding = 60-14.1 = 45.9m

so retardation = 30*30/2*45.9 = 9.8m/s2

case 2:-

retardatio = 9.8m/s2

distance travelled in 0.47s = 0.47*45 = 21.15m

no distance travelled while stopping = 45*45/2*9.8 = 103.32m

so total distance travelled = 103.32+21.15 =124.47m

explained in details now check it where you are doing wrong

hope it helps

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