Seasons greetings everyone. Merry Christmas and happy new year to all.
The brakes of a car can provide 6.5kN of force and the mass of the car is 1000kg. What is the stopping distance for car A traveling at 30km/h and car B traveling at 45km/h.
The answer in the book is A = 5.3m B = 12m
I did not get these answers and I can't figure out where I made the error. Please advise.
a=rate of change of speed = (v-u)/t
speed = distance / time = d/t
3. The Attempt at a Solution
For both cars f=ma
a=(6.5 x 103)/1000 = 6.5m/s2
Car A: 30km/h = 8.3m/s2
Car B : 45km/h = 12m/s2
Acceleration for car A: a=(v-u)/t
t=(v-u)/a t = (8.3-0)/6.5
t = 1.27s time to stop the car A
Acceleration for car B: a=(v-u)/t
t=(v-u)/a = (12-0)/6.5
t= 1.84s to stop the car B
speed=d/t so for car A distance = speed x time = 8.3 x 1.27 = 10.5m
speed=d/t so for car B distance = speed x time = 12 x 1.84 = 22m
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