Calculating Impact

Your best bet is to use the resources of your insurance company, Boss. After all, that's what we pay them for.

The doctor is merely offering an opinion.
The term 'factual estimate' is a contradicion in terms.

You can't 'calculate' the impact speed, a picture of the vehicle or a report from a vehicle inspector is probably evidence enough. Let others draw their conclusions.
Del

Ford Impala??????????

I was operating a 2002 Ford Impala.
Never heard of that car???????

Energy=Mass x Velocity^2

you need some sliding forces in there too but whos counting?

Yea! there is going to be some deflection when two different masses try to occupy the same space.

twisted metal too

Yep. We must also take into account the "heavy metal" factor. It can be quite distracting and add to the impact.

Energy = 0.5*Mass x Velocity^2

and F = m*a !

You'll need to know the weight of both vehicles.

Then it is simply a matter of using texasron"s formula.

Some reading for you:

Car Crash Example - HyperPhysics

accident reconstruction,engineering physics,speeds,distance,energy

Sounds to me that this is a setup for a law suit...

Maybe he is calculating that the offending vehicle weighed twice as much as the poor ford impala.....Insurance doctor math...

Nobody that has to ask a public forum how to calculate anything will have any legal standing in a reputable court.

This is an easy answer:

You were parked!

The other car was doing 35 mph or there abouts and did not brake!

The impact speed was 35 mph or there abouts whatever the other car was doing!

If you have an impact of 50 to 70 mph the other car was doing more!

End of story!

50-70 would only be possible if the OP's car were backing up at 23-35 MPH.

But the impact speed is still 70 mph. The effect might be different but to what extend?

Do you say you can not run away from bullets?

I rather meant that if the damage at OP's car sugggest that the impact speed was higher than 50-70 MPH was probabyl the driving speed of the other car.

I take it OP wants to verify the speed he was hit with. And the answer is what ever the other car was doing is the impact SPEED. And when there was no brakes applied the and OP was parked the impact speed is the same as the travel speed of the other car.

Now, if the question would have been impact force (which to a big extend it was not) then all the above explanations and points have to be taken into consideration.

Has OP come back at all?

You can't calculate the impulse without the change in velocity and the total time over which that change occurred.

You need an expert in forensic engineering that specializes in vehicle collisions....

http://www.waltersforensic.com/articles/accident_reconstruction/vol7-no1.htm

Your information is incomplete. What is the weight of the vehicle struck your vehicle - counts a lot in terms of force, since the Kinetic Energy of the hitting veicle is aborbed by the other one and the indent depends upon several factors like hardness resistance offerred by the vehicle- in terms of stationary on slope or moving in the same direction or moving in the opposite direction.

For the opposite side movement of vehicle, the relative speed will add up and hence Kinetic Energy also gets added up. Pl. post more details.

DHAYANANDHAN.S

Maybe OP was parked in the middle of the road, ie illegally, and is now trying to prove that the accident was not due to his "Ford Impalla" being stopped where it shouldn't be but due to the excessive speed of the other party so that he can actually make a claim for something which was the result of his own doing.

Or not. Just guessing unless OP comes up with another story.

This is the insurer's job....assuming the Impalla was insured that is.

Please answer the following questions, and excuse my ignorance of some matters.

1. Road conditions;

Were you parked on bitumen or dirt or gravel?

Was there gravel or lots of dirt on the bitumen?

Was it wet or dry?

2. The vehicles:

What is the weight of the Impala? (Chev?)

What is the weight of the other car? If you can't give weights, make and model of the other car, or how much heavier or lighter was the other car, percentage wise?

Is your car rear-wheel drive?

Is your car auto or manual?

Did you have your emergency brake on?

Does your emergency brake operate on rear brake shoes or prop shaft or what?

Can your emergency brake lock the wheels when you're moving or does it just slow you down?

Was your car in gear (or in Park position)? Which gear?

3. Immediately after impact:

Did you both continue in the same direction?

Did the 2 cars stay in contact until they came to rest?

Did you apply the foot brake?

Did the other car apply the foot brake?

How far did your car travel?

I forgot to ask:

Was your car on the flat, downgrade or upgrade? Details please.

There is no way in which a doctor's examination of the victims of this sort of accident could provide an accurate determination of the actual impact speed.. Your doctor's opinion is worthless. To arrive at any sensible conclusion you would have to have a report of the site conditions, photographs showing the presence or absence of braking marks, and views of the damage to both vehicles. This is all the province of a specialist who has access to a database of such reports, from which impact speeds can be estimated, not calculated.

I don't see what the speed at impact has to do with anything. You were parked, so the fault of the accident should be 100% on the other driver's car. Therefore he/she should pay for all damages and suffering.

Driving faster does not increase the percentage of responsibility, nor does it increasethe damages your car and family have already legitimately sustained.

Depends where you were parked....

If you are illegally parked then I think the rap is reversed.

eg double parked in the middle of a highway, around a bend and over a crest....your asking for it then.

Cars have to be crash tested before market and there are photos to show how much damage is done at x speed. Your insurer and/or the police will be able to better judge the impact speed from these. Your doctor may be right and further investigation may be warranted on his advice.

Jim

I was stopped on 3 lane highway due to traffic and was hit by vehicle doing about 80 km. Lot of damage to me and my vehicle. Speed means nothing, all you have to be aware of is (1) Before accident you had a good life. (2) After accident your life was not as good. Keep records of all treatment and a diary of how your life is on a daily basis. Never be definite on things like speed, do not use terms like always, never, absolutely. Listen to your lawyer as this is a cut and dried if your account is accurate.

Why would you want to calculate the impact? Would this calculation change the facts? Wasn't this investigated by the local officials? Can you not get a report from them? They do this calculation in the report, and it also contains the facts relating to the calculation of the speed. Might also explain why someone was traveling at speed where someone was parked. Otherwise read through these comments and you will find the formula for calculating the impact and you can put a pencil to this. Happy ciphering!

This thread highlights the need for vehicle on board cameras.

I have reviewed the blogs.

1. Known:

The other car did not brake.

2. Assumptions:

You had your foot on the brake the whole time.

You 4-wheel skidded to a halt in a roughly straight line.

You were on the flat.

The 2 car weights were little different from one another.

The cars remained together for the duration of the crash.

Coefficient of friction tyre to bitumen (no gravel, and dry) is 0.7.

3. Calculation:

Mass of one car = M

Mass involved in deceleration = 2 M

Frictional force resisting forward motion, one car only F = 0.7 M g

Where g = 32 ft/sec/sec

Deceleration rate a = Force/Mass = 0.7 M g / 2 M = 0.35 g

Velocity just after impact = sqrt(2 a s) = sqrt(0.7 g s) feet/sec

Where s is distance your car was moved (feet).

(note 60mph = 88 ft/sec)

By the principle of conservation of momentum, the offending vehicle was travelling (at least) at twice this speed before colliding with you.

I would like to add one more known; at time of impact inertia "caused" OP's foot to come off the brake for a time. adding distance travelled.

By the principle of conservation of momentum, the offending vehicle was travelling (at least) at twice this speed before colliding with you.

This does not make sense. If the speed was v just after impact and 2v just before the impact then the impact deceleration would have been enormous. In fact the speed would have been v just before impact and slightly less than v after impact. Moreover, this analysis applies only to an elastic collision. Because of the crumple zones built into both vehicles, a large amount (for us impossible to calculate) of the energy involved disappears into the crumpling.

The two cars will crash together and the velocity of the first car will be split between the two. The impact you are describing would be if there were no crash and the cars bounced off each other like billiard balls. In this case the second vehicle would travel at speed "v" while the first car acting as the cue ball would have velocity 0.

Sorry, please read what I actually said. "Because of the crumple zones built into both vehicles, a large amount (for us impossible to calculate) of the energy involved disappears into the crumpling." I too discounted the billiard ball analysis.

Conservation of Momentum:

Momentum before Impact = Momentum after impact

M*U =2*M*V whence V = U/2

M = mass, U = Initial Velocity, V = Final Velocity

Energy loss:

K.E. before Impact = 0.5*M*U^2

K.E. after Impact = 0.5*2*M*V^2 = 0.5*2*M*U^2/4 = 0.25*M*U^2

Half the KE has been used up in accelerating the front car, decelerating the rear car, and crumpling the panels.

Obviously this is idealised, but you can see what is happening from this example.

This is an extremely simplistic analysis, and helps not at all. For a start, momentum is conserved only in an isolated environment, e.g. a Newton's cradle. After the collision, with its associated crumpling, the velocity of both vehicles is zero. The combined momentum of the two vehicles can hardly be said to have been conserved, as it is also now zero. Likewise there is no point in writing equations for the velocities involved in kinetic energy equations without knowing how much energy is lost in the crumpling.

Note that I said IMPACT ie the moment when the two vehicles came together and became one. EVENTUALLY the momentum and K.E. fell to zero, but at the moment of IMPACT there was still lots of it to go around.

Yes it is simplistic, but I wanted to give you a general idea of what was happening. It was not my intent to say THIS IS EXACTLY WHAT HAPPENED.

Sorry, this is still less than impressive. If you are only considering the instants before and after impact, then yes, the momentum and kinetic energy have hardly changed, but still they cannot be calculated. Furthermore, it is not just half the kinetic energy which goes into "accelerating the front car, decelerating the rear car, and crumpling the panels". All the kinetic energy goes into that process, and at the end the KE is zero.

Enough of this! just enter the values and presto, an answer.

http://hyperphysics.phy-astr.gsu.edu/hbase/carcr.html#cc1

That's nice but everything needed to be known for this calculation is unknown. The speed of the moving vehicle is in question. The proffered make and manufacturer of stationary vehicle is wrong. The make and manufacturer of the moving vehicle is unknown along with its mass. The mutual destructive force between vehicles is unknown. The only thing we plausibly know is that a thirteen year old parked vehicle suffered more damage than it is worth ($3000?).

Its amazing that we all studied engineering, physics, etc. and cannot come with an answer. We should have gone to med school and in 5 minutes, 70 mph!

Or become insurance actuaries, where we could come up with the same result, any time it suited us. Or the opposite result, if THAT suited us.

Who knew Doctors got their training from insurance schools?

But then, the Doctors only know half as much as the actuaries, since they can't get but one result, each, while the actuary can quote any result that he/she likes NOW, and a different one later. Nice skill to have!