- #1

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It was a CHP in san diego and i'm pretty sure they drive the crown vic???

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- Thread starter iminsandiego
- Start date

- #1

- 4

- 0

It was a CHP in san diego and i'm pretty sure they drive the crown vic???

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- #2

- 1,179

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You cannot answer this question without knowing how long it took to reach 110 mph.

- #3

- 2,685

- 22

Regardless, surely it's irrelevant. If you were still accelerating away from them once they hit 110, you were clearly going faster than them. All the math in the world won't help you.

- #4

Pengwuino

Gold Member

- 4,989

- 16

What the hell were you doing going 150mph??

- #5

- 2,685

- 22

What the hell were you doing going 150mph??

Trying to get away from a cop car......

I love how people try to worm their way out of it when they get caught.

- #6

K^2

Science Advisor

- 2,469

- 29

Just for fun of it, lets see. Police Crown Victoria tops out at about 130 mph. Lets assume that at that speed power dissipated to drag equals power delivered by engine. Lets also assume that drag is purely quadratic in speed and that engine always operates at peak power during the 0-110mph acceleration. Yes, I know, that last one is going to make it a bit off, but without going into actual gear ratios of the cruiser, which I can't be bothered to look up, that's the best we can do.

So all in all, very rough estimate, but there is some physics in it.

Engine power: P = 250HP = 186kW

Vehicle mass: m=1700 kg.

Top speed: 130mph = 58m/s

Target speed: 110mph = 49m/s

Power dissipated to drag is given by kv³, and we know it to be equal to engine power at top speed.

Power coefficient: k = 0.953 kg/m.

At any given speed, the force is given by available power over speed.

F = (P - kv³)/v

Hence, the acceleration:

a = P/(mv) - kv²/m

The analytic solution to this equation is so ugly that I want nothing to do with it. On the plus side, numerical solution is easy.

I'm getting 545m traveled in 15s by the time it hits 110mph. That's almost exactly 1/3rd of a mile. Though, 15s is just a touch too fast for 0-110mph. It should take closer to 20s. So the actual number will be a bit higher. Maybe 1/2 of a mile or so.

So all in all, very rough estimate, but there is some physics in it.

Engine power: P = 250HP = 186kW

Vehicle mass: m=1700 kg.

Top speed: 130mph = 58m/s

Target speed: 110mph = 49m/s

Power dissipated to drag is given by kv³, and we know it to be equal to engine power at top speed.

Power coefficient: k = 0.953 kg/m.

At any given speed, the force is given by available power over speed.

F = (P - kv³)/v

Hence, the acceleration:

a = P/(mv) - kv²/m

The analytic solution to this equation is so ugly that I want nothing to do with it. On the plus side, numerical solution is easy.

I'm getting 545m traveled in 15s by the time it hits 110mph. That's almost exactly 1/3rd of a mile. Though, 15s is just a touch too fast for 0-110mph. It should take closer to 20s. So the actual number will be a bit higher. Maybe 1/2 of a mile or so.

I think he's hoping that they'd knock off 10mph or so if he can "prove" that the cop car couldn't get to 110. Difference in fines at 100 and 110 tends to be significant. (I don't know exact rates in Cali.) Problem is, he's likely to dig himself in deeper if he tries to defend. If it's just a fine, he should go with no-contest, pay the fine, and be glad that's all it cost him. I have a feeling that if the cops actually show up at the hearing, this guy won't be keeping his license.Regardless, surely it's irrelevant. If you were still accelerating away from them once they hit 110, you were clearly going faster than them. All the math in the world won't help you.

Last edited:

- #7

- 2,544

- 3

im just curious why were you going 150 .

- #8

Ranger Mike

Science Advisor

Gold Member

- 2,168

- 228

we always picked a desolate deserted strip with no access by farm tractors or small children ( you probably did not and chose to randomly speed - strike two)

we were prepared to WALK if we got snagged by the local fuzz and realized driving was a privilege and not a right, so if we got popped don't cry...( strike three)

we made sure the TIRES and steering, suspension were in excellent shape so as not to endanger us or each other ( i doubt you did - strike 4)

we knew the dangers of front end float once you passed 120 mph ( we knew the limits of our vehicle and where the red zone was- again, i doubt you know this)

YOUR OUT- out of luck, out of a car and out for a long time walking

- #9

- 2,017

- 85

Can we ban the OP for being an idiot?

- #10

- 4

- 0

Again THANKS

Just for fun of it, lets see. Police Crown Victoria tops out at about 130 mph. Lets assume that at that speed power dissipated to drag equals power delivered by engine. Lets also assume that drag is purely quadratic in speed and that engine always operates at peak power during the 0-110mph acceleration. Yes, I know, that last one is going to make it a bit off, but without going into actual gear ratios of the cruiser, which I can't be bothered to look up, that's the best we can do.

So all in all, very rough estimate, but there is some physics in it.

Engine power: P = 250HP = 186kW

Vehicle mass: m=1700 kg.

Top speed: 130mph = 58m/s

Target speed: 110mph = 49m/s

Power dissipated to drag is given by kv³, and we know it to be equal to engine power at top speed.

Power coefficient: k = 0.953 kg/m.

At any given speed, the force is given by available power over speed.

F = (P - kv³)/v

Hence, the acceleration:

a = P/(mv) - kv²/m

The analytic solution to this equation is so ugly that I want nothing to do with it. On the plus side, numerical solution is easy.

I'm getting 545m traveled in 15s by the time it hits 110mph. That's almost exactly 1/3rd of a mile. Though, 15s is just a touch too fast for 0-110mph. It should take closer to 20s. So the actual number will be a bit higher. Maybe 1/2 of a mile or so.

I think he's hoping that they'd knock off 10mph or so if he can "prove" that the cop car couldn't get to 110. Difference in fines at 100 and 110 tends to be significant. (I don't know exact rates in Cali.) Problem is, he's likely to dig himself in deeper if he tries to defend. If it's just a fine, he should go with no-contest, pay the fine, and be glad that's all it cost him. I have a feeling that if the cops actually show up at the hearing, this guy won't be keeping his license.

- #11

- 4

- 0

Im a corporate pilot for my profession I work on my car and doubt you have the formal training to preflight your car the way i do mine. You never draged if you didnt get above 150unless it was in your bug. In comparison to my skill in the high speed realm that makes you very unsafe and you shouldnt drive over the limit.

Good thing opinions of mighter than thou ness are just those and just like A__holes everyone has one

Cheers

we always picked a desolate deserted strip with no access by farm tractors or small children ( you probably did not and chose to randomly speed - strike two)

we were prepared to WALK if we got snagged by the local fuzz and realized driving was a privilege and not a right, so if we got popped don't cry...( strike three)

we made sure the TIRES and steering, suspension were in excellent shape so as not to endanger us or each other ( i doubt you did - strike 4)

we knew the dangers of front end float once you passed 120 mph ( we knew the limits of our vehicle and where the red zone was- again, i doubt you know this)

YOUR OUT- out of luck, out of a car and out for a long time walking

- #12

- 4

- 0

Regardless, surely it's irrelevant. If you were still accelerating away from them once they hit 110, you were clearly going faster than them. All the math in the world won't help you.

"Never submit and show your soft underbelly" -Me, 2011

"only dogs lay down and submit" -Me, 2011

"Math" Math"- Me-2011

- #13

- 2,544

- 3

when you were drag racing did you win ?

- #14

- 2,685

- 22

Ooh you're a pilot, big wow. Being a pilot does not make you something special when it comes to driving. Heck, I know pilots who don't know the first thing about cars. So let's stop making utter BS remarks about your "skill in the high speed domain".

You've admitted you were caught at 150mph. Suck it and accept it.

Don't get sh*tty with people here. You come here, asking for us to help you get out of breaking the law and expect people to just accept it?

"only dogs lay down and submit" -Me, 2011

Tell the cop that next time you're caught at 150 and he pulls his piece on you.

"Math" Math"- Me-2011

Then I suggest you learn it.

- #15

Pengwuino

Gold Member

- 4,989

- 16

What kinda person quotes himself?

- #16

- 2,685

- 22

What kinda person quotes himself?

I'm thinking of someone with a Kim Jon-Il style attitude about themselves.

- #17

- 2,017

- 85

Also OP it's not becuase you drove fast, it's because you failed enough to get caught doing it. Making you a moron.

- #18

- 2,685

- 22

Calling a public vote for ban.

Motion seconded.

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