# As physics

posted by Jan

The table below shows how the braking distance x for a car depends on its initial speed u
u / ms-1 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= 30ms-1.

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.

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

1. 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

2. 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

## Similar Questions

1. ### AP Physics

To stop a car, you require first a certain reaction time to begin braking. Then the car slows under the constant braking deceleration. Suppose that the total distance moved by your car during these two phases is 56.7 m when its initial …
2. ### Physics

To stop a car, you require first a certain reaction time to begin braking. Then the car slows under the constant braking deceleration. Suppose that the total distance moved by your car during these two phases is 56.7 m when its initial …
3. ### As physics

The table below shows how the braking distance x for a car depends on its initial speed u u / ms-1 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= 30ms-1. The …
4. ### As physics

The table below shows how the braking distance x for a car depends on its initial speed u u / ms-1 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= 30ms-1. The …
5. ### physics As

How do you calculate the braking distance?
6. ### As physics

How do you calculate the braking distance?
7. ### physics As

The table below shows how the braking distance x for a car depends on its initial speed u u / ms-1 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= 30ms-1. The …
8. ### As physics

Q11.The table below shows how the braking distance x for a car depends on its initial speed u. | u / ms-1 | 5 | 10 | 20 | 40 | | X / M | 2 | 8 | 32 | 128 | The relationship between x and u is: doubling speed increases distance by a …
9. ### Physics

Q11.The table below shows how the braking distance x for a car depends on its initial speed u. | u / ms-1 | 5 | 10 | 20 | 40 | | X / M | 2 | 8 | 32 | 128 | The relationship between x and u is: doubling speed increases distance by a …
10. ### Damon/BobPursley/Physicstutor/whichoneisright

Q11.The table below shows how the braking distance x for a car depends on its initial speed u. | u / ms-1 | 5 | 10 | 20 | 40 | | X / M | 2 | 8 | 32 | 128 | The relationship between x and u is: doubling speed increases distance by a …

More Similar Questions