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"Anyone here really good at physics? Hopefully you can help me"

Here's the story.....

A car has been caught in a box junction by police and you need to contest that you couldn't have stopped before entering it. I have the following info:

Width of junction: 8m
Time orange light displayed: 3s
Speed Limit: 30mph
Car length: 2m

I'm taking for fact that the car has 120 horsepower=90 kW
and that the car weighs 1000kg

Any ideas what to do next?

Thanks, and please if you can't help, dont reply or mess up the thread. Cheers.

Notorious Biggles wrote:
> Here, I had a go, hopefully you can get something out of this.
>
> 1 mile ~= 1.6093 kilometres
> = 1609.3 metres
>
> speed in metres per second is (30*1609.3) / 3600 (number of seconds
> in hour)
>
> a = v - u / t
> a = 0 - 13.410833... /3
> a = - ~4.4703 ms^2

Thats the figure I got for a
>
> s = ut + 1/2at^2
> s = 40.2325 + 1/2 x - ~4.4703 x 9
> s = 20.11625 m would be the distance from car to lights if it could
> stop in time. Maybe.

For this I got 32.52m
>
> I've now lost track of where I was going with this. Bah.
>
> I may be wrong, but I doubt you should have to research anything to
> be able to solve this.

Thanks. I handed it up today so hopefully the answer I got was right.

Here, I had a go, hopefully you can get something out of this.

1 mile ~= 1.6093 kilometres
= 1609.3 metres

speed in metres per second is (30*1609.3) / 3600 (number of seconds in hour)

a = v - u / t
a = 0 - 13.410833... /3
a = - ~4.4703 ms^2

s = ut + 1/2at^2
s = 40.2325 + 1/2 x - ~4.4703 x 9
s = 20.11625 m would be the distance from car to lights if it could stop in time. Maybe.

I've now lost track of where I was going with this. Bah.

I may be wrong, but I doubt you should have to research anything to be able to solve this.

Width of the junction? Actual width would be irrelevant, do you mean thd distance from one side to the other in the direction the car is travelling?

Yes

Is this degree level?

Aoe wrote:
> Don't you kind of have to do this yourself?

I couldn't. Thats why I turned to here for some help.

English_Bloke wrote:
> Don't you need stats like, distance the car was from the junction when
> the lights changed, speed the car was going and such?

A lot of it is based on assumptions, such as you assume the car is travelling at the speed limit of 30mph. We weren't told distance so I guess somehow i have to figure out the distance travelled in 3 seconds or less seeing as the car went through an orange light.

Don't you need stats like, distance the car was from the junction when the lights changed, speed the car was going and such?

Don't you kind of have to do this yourself?

You can pass through an orange light when the lights are changing, but you're supposed to slow down and not go through if you have time to stop. I have to prove the car didn't have time.