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Anonymous Poster #1

# Three Car Collision. Force of Impact Calulations Needed.

02/15/2017 6:44 PM

Hey guys, I'm going to say right up front that I haven't a clue how to do these calculations, but I have a scenario that I would like the math to if anyone can help me figure it out. What I had been able to attempt to figure out doesn't seem tangible? In the scenario I will supply both the US customary system and the metric system so you can choose what set of numbers you'd prefer to work with.

Here goes:

Imagine that there is a 3 car accident. A compact car (2,425.1 lbs./1,100 kg) is making a left turn at 35 mph/56.327 km per hour. The car is hit on its side, just behind the passenger door, by a midsize car (3,154 lbs./1,430.63 kg) traveling at 44 mph/70.81 km per hour. Then a midsize SUV (4,094 lbs./1,857.01 kg) barrels through going 57 mph/91.73 km per hour. A rough estimate of impact damage to each vehicle is as follows: Compact Car (5ft./1.524m), Midsize Car (Front-4ft./1.2192m, Back-6ft./1.8288m), and the Midsize SUV (6ft./1.8288m).

Now here's my question(s); 1) How much force (force of impact) would be applied to the compact car from the overall collision, and 2) Would that impact send the compact car into a rollover, and if so how far would it travel?

If any other information is needed, let me know and I'll do my best to supply that. Thanks in advance you guys!

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#1

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 6:49 PM

I hope somebody's verdict of guilt or innocence doesn't hinge on what you find here, because this is exactly the sort of question a lawyer would ask. Contact a physicist who specialises in forensics of this sort.

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#2

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 6:53 PM

I know it's an odd question. I'm actually writing a fictional novel and I'm trying to give some credibility when came down to the nitty gritty details.

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#3

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 7:00 PM

There is a lot more to these sorts of problems than meets the eye. For instance, cars crush and absorb some of that impact. How, how much, and where they crush can radically alter where they end up and how fast. Slide sideways? Spin? Flip? Cars are not billiard balls. The kinetics of such collisions are very complex.

My recommendation is to search court records of cases involving similar collisions and wing it from there.

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#12

### Re: Three car collision. Force of Impact Calulations needed.

02/16/2017 12:40 AM

Since its is fictional

...the third car took off and rolled over impacting 6.5 m behind the incident scene. The two other cars got stuck to each other, mended by the third impact in a t-boned shape. None made it out alive but the driver from the rolled car because the driver was flung out from the open window.

btw it rolled two times mid air and came to rest on the broken wheels.

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#4

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 7:55 PM

either this is a poorly veiled lie or an incredibly boorish novel.. even from an engineering standpoint.

Way WAY WAY to many details to be a novel.. Who in the world would call you out for improper details for an accident in a novel ?! Makes zero sense. I''m insulted

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#6

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 8:01 PM

I'm very thorough, plus this isn't supposed to be an exciting deal. It's meant for boring insurance talk. The math itself won't be in the novel, just the actual answer. Don't be insulted, this is actually a topic that I've been wondering about for a while too, so it does give me an extra initiative to seek out this generalized answer. Writing the details of the crash is easy, having numbers behind it helps me to ensure that my scenario is plausible. 'Tis all :)

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#11

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 9:49 PM

Each vehicle is constructed differently and will crush differently depending on where it's hit and by what. Where did you come up with numbers for the crush depth? Why aren't you asking if those numbers are plausible? How did you come up with specific weights for each vehicle? and what did the SUV hit? Where? All I'm saying is that for being a very thorough novelist there is an awful lot to be desired.

In a fiction novel you can pretty much write what you want and not be called out.. Unless your readers are very picky crash investigators excellent with physics.

make the car roll if you want. In real life it would either roll or not. it will be a better read if it rolls.

I'm not really insulted so much as incredulous, but I'll give you the benefit of doubt and think you must be quite the freak of a novelist with a peculiar interest in crash force.. So that can only be a good thing.

welcome to the forum btw

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#28

### Re: Three car collision. Force of Impact Calulations needed.

02/17/2017 3:04 PM

how about the pavement is it concrete, asphalt? is it wet or frozen? is the ground level? the amount of tread on the tires, air temperature, did the drivers apply brakes? at what millisecond? did the driver(s) turn the wheel to avoid colision? at what millisecond? where is the center of gravity in each vehicle? shape of the vehicle... to many variables to get a concise answer to your problem.

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#31

### Re: Three car collision. Force of Impact Calulations needed.

02/17/2017 3:55 PM

You forgot to factor in the difference between a duck, and not ducking.

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#5

### Re: Three car collision. Force of Impact Calculations needed.

02/15/2017 7:57 PM

If an object goes from a given speed to zero speed within a certain distance, its average acceleration can be computed. From there, F=ma can give the impact force. The relevant speeds involved will depend on angles of impact, not just the "straight" speeds of the individual vehicles.

In a novel, you wouldn't want to deal too closely with trig complications. That makes it challenging as to how to say enough without having to say too much.

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#7

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 9:28 PM

You want to calculate force. There are two physical equations involving force:

1. change in momentum = force x time

2. change in energy = force x distance

The second equation is what you need here.

The kinetic energy of the moving car in the collision is 1/2 x mass x velocity squared. When a moving car collides with the stationary one, there is a "crush distance". The average force = the kinetic energy divided by the crush distance.

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#8

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 9:33 PM

This is awesome! That was the formula I had found, but I wasn't sure if it was the one I was looking for! Thank you so much for your help!

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#9

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 9:45 PM

Whether the small car would roll over depends on its track width, the location of its center of gravity, and the coefficient of friction of the tires, and the height that the collision force is applied. If the couple of the collision force and the tire friction force is enough to lift the center of gravity vertically above the wheels, it would roll over.

It's hard to calculate how far it would roll.

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#10

### Re: Three car collision. Force of Impact Calulations needed.

02/15/2017 9:48 PM

You are AHH-MAZING!!! My scenario looks like it'll pan out after all! Another many many thanks to you!!

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#14

### Re: Three car collision. Force of Impact Calulations needed.

02/16/2017 10:57 AM

You are not writing for a new episode of "Bull" are you? What mitigating circumstances are present for the driver of vehicle #1?

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#19

### Re: Three car collision. Force of Impact Calulations needed.

02/17/2017 4:49 AM

"and the height that the collision force is applied."

And the "effective" coefficient of friction between the two colliding vehicles: it's easy to imagine a scenario where part of the large vehicle slides under part of the smaller and flips it over; on the other hand part of the larger vehicle may slide over part of the smaller and hold it down and result in the larger vehicle turning over, or, part of the larger vehicle might "dig in" to the smaller so that no slipping occurs.

To the OP: what about a picture? Don't forget to include (in the novel) lots of details about the analysis of the skid marks, that's how the forensic guys always work out what really happened in an accident.

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#13

### Re: Three car collision. Force of Impact Calulations needed.

02/16/2017 3:57 AM

No dash-cam, then?

There are loads of collision videos available for further study on . One might easily copy one of those into fiction.

For some reason, most of them happen in Russia.

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#15

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/16/2017 11:24 AM

Use momentum and impulse concept. You could model it in matlab or phyton in a very simplistic approach.

The roll-over thing is a sort of complicated task to simulate. This can be done with Finite Element Analysis, though there might be some open sources in the internet specialising impact and collisions of cars in 1D,2D or 3D perhaps. I don't know. Use google.

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#16

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/16/2017 11:29 AM

I drive a sports car, the CG is very low and a side impact would , more than likely, just slide the car opposite the impact. A tall mini van or smart car might roll over(higher CG). There are many factors which would have to calculated in.

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#20

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 6:10 AM

<...sports car....> Those things tend to get pushed underneath other vehicles instead of impacting them.

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#17

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/16/2017 3:57 PM

Do any of the specific car makers have available test data on any of the individual types of collisions?...

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#18

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 4:12 AM

As you have stated, it is imaginary and fictitious so anything may occur that you want write about. I think what you may be more interested in is, would the right person survive your idea.

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#21

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 6:22 AM

I'm in the auto field and I have some comments for you that you may find helpful.

1. A compact car cannot make a left turn at 35mph.

2. To make your story more exciting, I'd have a full size SUV (Tahoe or Suburban) ram into the right rear quarter panel of the lowly Chevy Aveo (compact car). At 44 mph, the Aveo would go airborne and fly into the shop window of a bakery. Gasoline would start leaking and soon you'd hear an explosion! Booom! Bang! Kabooooom! People would be running out of the bakery with the pastry chef coming out in flames. People on the street would be screaming! Kids would be crying! A bystander would take of his jacket and cover the burning chef, then roll him on the ground! After impact, the Suburban would lose brake power and would roll, uncontrollably down the street toward the school playground. The driver laying on the horn, when out of nowhere, an 18 wheeler full of Leekweed Nitrogen would lock up its brakes and jackknife toward the Suburban. Bam! The Suburban is crushed and the tank of explosives has now flipped on its side and is sliding toward a metal foundry! EEEEKKKKKKK as the truck slides toward molten steel! Then out of nowhere a CHP officer rides by on his motorcycle, but it's not an ordinary CHP officer - it's a T-3000! Blam, Blam, Blam - he's shot with a 12g - buckshot blasting a hole, right through his abdomen and his right arm is dangling! Sluurrrp, that's Leeeeekweeeeed meddul. The T-3000 reforms himself into a CHP officer - oh no! The tanker full of Leekweed Nitrogen has cracked open and the T3000 is waking right through it! First his left leg freezes and falls off. Next his right. Then his abdomen falls to the ground and explodes into tiny frozen pieces of frozen metal. But the heat! The heat from the smelting! The temperature rises and the shards of metal are melting into silvery balls - like when we were kids and we played with a broken thermometer! The silvery balls roll into larger balls and slowly the T-3000 takes shape again into a CHP officer. YOU CAN'T KILL THIS THING!!!!

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#27

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 2:54 PM

Terminate it.

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#37

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/22/2017 3:49 AM

I'll be bock!

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#22

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 6:38 AM

As your idea is fictitious, I don't see how your idea will be to what you may think. Your scenario will induce spin in the 1st vehicle in the opposite to travel. The vehicle impacting the 1st car will veer right, (assuming you are driving a vehicle on the left side of the road). Both vehicles would theoretically spin away from the impact in the opposite direction of travel.

The 3rd vehicle would have in effect a gap to ingress. So your calculation needs to be initial impact on 2 vehicles, one of which receives a 2nd impact in either direction of the spin, T boned on one side, there is more chance the vehicle will go upwards more than travelling a distance.

To obtain your scenario, logic says that the 3 vehicles would need to collide within split seconds of one another meeting on the junction. The creditability is then lost, as why would a driver turn out into two oncoming vehicles, so close to him?

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#23

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 8:23 AM

Here's the full scenario I was thinking of:

Car #1 (2 passengers) is driving semi-close behind an ambulance because a loved one is being transported to the nearest hospital. Of course, when an ambulance is active, people have to steer to the side of the road and wait for it to pass. So here is when the crash occurs. The ambulance turns into the community hospital complex, Car #1 on its tail traveling at 35 mph. Car #2 (driver only) is coming toward them, unaware of Car #1, thinking it can out run the ambulance before it turns traveling at 44 mph. The ambulance completes the turn, but Car #2 collides just behind the front passenger seat of Car #1. This causes a slide, but immediately after the initial collision, Car #3 (SUV; 6 passengers) strikes the back of Car #2 at 57 mph.

Now, I was thinking that the force of the slide begins the momentum. Car #3's impact is initiated, pushing Car #1 to the curb, which would cause a single rollover, making Car #1 flip onto its hood.

Hopefully this gives much better context.

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#24

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 8:33 AM

Car #1 is similar to the 2005 Toyota IST

Car #2 is similar to the 2008 Mercury Milan Premier

Car #3 is similar to the 2007 Suzuki XL7

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#36

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/22/2017 3:47 AM

IDK, I'm sorry, but I don't know what a Toyota IST is.

Second, a 2008 Mercury Milan Premier should be in the junk yard. It's 9 years old if it has normal miles, it would have 135K on it. I don't think it would be running at this point.

Third, a Suzuki XL7 isn't that much heavier than a Mercury Milan (500-600 lbs). Also, there are so few of these on the road, so having an accident occur with a Milan and XL7 is very unlikely.

I think a better choice would've been using the following cars for the wreck.

1. 2013-15 Toyota Corolla LE - there are tons and tons of these cars on the road.

2. Midsize car is a Toyota Camry LE - The number one selling car in the US for 15 straight years!

3. SUV - you need something bid. Hey, there are tons of those big 2001 to 2006 Chevy Tahoe's on the road now and they're heavy beasts.

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#25

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 8:42 AM

And how does force of impact # make this credible or not? Nothing is predictable is any such scenario. If you tried to repeat the crash a dozen times you would have a dozen outcomes. Add that line to your book.

You were spot on for booring. Add a flaming bakery and I'll buy a copy.

Good luck in whatever this is actually about.

What author has inspired you the most?

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#26

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 11:34 AM

I will gladly take that line.

I'm not sure the overall story would be your cup of tea lol, but thank you for your opinion :)

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#29

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 3:08 PM

What is tealol? So this is all about sex, scandal, murder, money, scandal and sex and the UK NHS!

You can get all that and more on this site, daily.

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#33

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 9:51 PM

I was typing really fast haha! It's was supposed to be "cup of tea, lol!" But its definitely centered around sex, money, and scandal of a high profile family. The main character is the fiancé of the high profile guy who is very unhappy that she drunkenly accepted his marriage proposal.

How I initially started writing out the plot actually turned into a niche where the story is told from 3 points of view, all in first person. It's something that I'm currently trying to work out how to operate.

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#30

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 3:53 PM

Forget having the baker run out aflame. Save the donuts!! I see them rolling out on fire - caramel fire that is!!!!

DOH!!!

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#32

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 5:26 PM

DOH!!! KNUT.

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#34

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/17/2017 11:59 PM

I remember reading this very question in a chapter of an Algebra 1 student textbook.

In fact, every chapter in that book started off with a hypothetical fictional scenario.

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#35

### Re: Three Car Collision. Force of Impact Calulations Needed.

02/20/2017 9:13 PM

I think you might get more attention if you include a scene similar to the unfortunate results of a certain rear-end collision that was amply described in the novel "The Hotel New Hampshire" by John Irving.

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