As physics
posted by Jan
The table below shows how the braking distance x for a car depends on its initial speed u
u / ms1 5.0 10 20 4
x / m 2.0 8.0 32 128
the reaction time of a driver is 0.60s. Calculate the sopping distance of the car when u= 30ms1.
The mark scheme says:
Thinking distance= 30 X 0.6 =18m which I understand fully.
BRAKING DISTANCE =0.08 * U^2= 0.08 * 30^2= 72m IS THE BIT I DON’T UNDERSTAND. CAN SOMEONE PLEASE EXPALIN THE BRAKING DISTANCE STAGE AND WHY AND HOW YOU DO THIS BIT AS WELL AS ALL EQUATIONS INVOLVED!
Stopping distance= 18 +72= 90m which I understand fully.
please help.
Explain the working out of the braking distance for this question.
As physics  cylinder Thursday, November 9, 2017 at 7:37am
I wrote what I do know and the caps lock is what I dont know, and that is the working out for braking distance shown above is confusing to me.
As physics  Damon Thursday, November 9, 2017 at 8:39am
your table makes no sense to me
v = Vi + a t where t is AFTER 0.6 s
v = 30 + a t
so
x = Xi + Vi t + (1/2) a t^2
a will be negative of course
Xi is 18 when t = 0
x = 18 + 30 t + (1/2) a t^2
remember total stopping time = t + .6
As physics  cylinder Thursday, November 9, 2017 at 9:27am
I am in as and we dont use those symbols so im confused

Jan
Sorry for the repost i didnt understand and i just wanted to show how the working and answer went so someone can better help me

Jan
I had this question too and didnt understand it either when i went through thisquestionin a level we dont usae Xi or any of those please write in ful lsentencs ad clearly explain
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