Crash between 60mph car and 120mph car

[fleabag]

I'm not sure how to formulate this scenario but I will try. A car hitting another car at 60mph, with the same weight, size, design etc will the the equivalent of one of those cars hitting a brick wall at 60mph. Simplified, a car hitting a wall, the passenger moves forward towards the steering wheel (front of car) because the car has stopped but the person is still going in the same direction. Now if a car is going backwards at 60mph straight into a wall, when the car hits the wall, the driver is "still moving" and so hits the headrest since the driver is still moving while the car is not anymore.

Now for the real question. Let's first assume that you a car that can keep the passenger space perfectly intact all the way upto 150mph (i.e no intrusion that would hurt the passenger) and that the only reason the passenger would die is because of the sudden deceleration. With two of these identical cars, you take car "A" that is driving 60mph in a straight line and then take car "B" driving 120mph in straight towards car "A" going 60mph. Again, assuming that both cars are identical, would the passenger in car "A" feel like as though nothing happened (except for sound, broken glass etc.) since 60mph forward at first would make him go forward, but then you have 60mph backward which would be the equivalent of getting rearended and because of that, they should theoretically cancel each other out, right?

 

[masteryoda34]

Force is what would cause damage to a person in a car. Force = mass x acceleration. (Newton's second law). Acceleration is a change in velocity over time. The person in car A would experience a change in velocity from +60mph to -60 mph. Therefore, they would have a (likely deadly) force exerted on them.

 

[PowerEngineer]

If I understand your scenario correctly, we have car A at 60 mph being hit head-on by car B driving the opposite direction at 120 mph. If this collision were completely inelastic and the two cars locked together on impact, then I'd expect that car A would go from +60 mph to -30 mph. Since car collisions are clearly not inelastic (energy being dissapated in deformation), then the actual speed would be less negative (i.e. magnitude less than 30). In any event, the driver in car A would experience a delta V of around 80-90 mph in just a couple of seconds. Ouch...

 

[mpilchfamily]

So basicly the person in car A would fly threw the windshield of car A and colid with the widsheild of car B at about the same time as the driver of car B would hit car B's windsheild. While driver B is laid out on the hood of his own car driver A would be in the back seat of car B.

 

[Foxery]

God, my eyes.

PowerEngineer got it exactly, so I'm not sure what you're asking now. After the crash, both cars would still be rolling, (in the direction that the faster car was moving,) and both drivers would certainly be dead from the impact.

 

[Comdrpopnfresh]

Forget the person getting injured from an impact- that much impulse would make their hear detach from their arteries- the heart is a very dense muscle... more mass... sometimes race car drivers get out of an accident without a scratch, but die 10 minute later from a detached artery or some such.

 

[fleabag]

Originally posted by: PowerEngineer

If I understand your scenario correctly, we have car A at 60 mph being hit head-on by car B driving the opposite direction at 120 mph. If this collision were completely inelastic and the two cars locked together on impact, then I'd expect that car A would go from +60 mph to -30 mph. Since car collisions are clearly not inelastic (energy being dissapated in deformation), then the actual speed would be less negative (i.e. magnitude less than 30). In any event, the driver in car A would experience a delta V of around 80-90 mph in just a couple of seconds. Ouch...

Why would they experience a delta V of 80-90mph? Why isn't it that the car could experience a high change in velocity but not the occupant?

 

[Foxery]

Dunno what you're imagining, but most cars have a steering wheel, the frame, and an engine between you and the road. Passengers may push through the windshield, but drivers are restrained by the steering wheel. (Not to mention seat belts.) Remember, your body is effectively wrapped around it in a "C" shape. Your legs have nowhere to go.

 

[BrownTown]

Originally posted by: fleabag

Originally posted by: PowerEngineer

If I understand your scenario correctly, we have car A at 60 mph being hit head-on by car B driving the opposite direction at 120 mph. If this collision were completely inelastic and the two cars locked together on impact, then I'd expect that car A would go from +60 mph to -30 mph. Since car collisions are clearly not inelastic (energy being dissapated in deformation), then the actual speed would be less negative (i.e. magnitude less than 30). In any event, the driver in car A would experience a delta V of around 80-90 mph in just a couple of seconds. Ouch...

Why would they experience a delta V of 80-90mph? Why isn't it that the car could experience a high change in velocity but not the occupant?

Just think about what your saying there dude... If you and the car are going the same speed and then the car suddenly changes its speed by 90mph, how could you NOT change the speed jsut as fast? Either you accelerate by 90mph as well (and your internal organs turn to mush) or you go flying out the front of the car (and turn into a bloody smear on the pavement)...

 

[DrPizza]

Originally posted by: PowerEngineer

If I understand your scenario correctly, we have car A at 60 mph being hit head-on by car B driving the opposite direction at 120 mph. If this collision were completely inelastic and the two cars locked together on impact, then I'd expect that car A would go from +60 mph to -30 mph. Since car collisions are clearly not inelastic (energy being dissapated in deformation), then the actual speed would be less negative (i.e. magnitude less than 30). In any event, the driver in car A would experience a delta V of around 80-90 mph in just a couple of seconds. Ouch...

But, that's what an inelastic collision is: energy is dissipated. In an elastic collision, kinetic energy isn't lost. Due to conservation of momentum the car should still travel backwards at 30mph, except for momentum transferred to the earth during the collision through frictional forces against the road surface.

 

[PowerEngineer]

Originally posted by: DrPizza

Originally posted by: PowerEngineer

If I understand your scenario correctly, we have car A at 60 mph being hit head-on by car B driving the opposite direction at 120 mph. If this collision were completely inelastic and the two cars locked together on impact, then I'd expect that car A would go from +60 mph to -30 mph. Since car collisions are clearly not inelastic (energy being dissapated in deformation), then the actual speed would be less negative (i.e. magnitude less than 30). In any event, the driver in car A would experience a delta V of around 80-90 mph in just a couple of seconds. Ouch...

But, that's what an inelastic collision is: energy is dissipated. In an elastic collision, kinetic energy isn't lost. Due to conservation of momentum the car should still travel backwards at 30mph, except for momentum transferred to the earth during the collision through frictional forces against the road surface.

You are right. I reversed elastic and inelastic. My bad...

Too many years since first year physics.

 

[PlasmaBomb]

Originally posted by: Foxery
God, my eyes.

This.

Originally posted by: fleabag
Let's first assume that you a car that can keep the passenger space perfectly intact all the way upto 150mph

They both die because the collision speed is 180 mph...


As for the second part...

You might as well say that car A is stationary, and gets hit head on by car B at 60, whilst simultaneously being rear ended by car C at 60... would the passenger in car "A" feel like as though nothing happened...

Originally posted by: fleabag
Why would they experience a delta V of 80-90mph? Why isn't it that the car could experience a high change in velocity but not the occupant?

First question - the law of conservation of momentum

Wiki

Second question - the occupant would experience the same change in velocity, the trick to them surviving it is for it to happen more gradually (assuming they don't get squashed).

More information on g-forces

Highest g-forces survived by humans

Voluntary

Colonel John Stapp in 1954 sustained 46.2 g in a rocket sled, while conducting research on the effects of human deceleration.

Involuntary

Formula One racing car driver David Purley survived an estimated 179.8 g in 1977 when he decelerated from 173 km/h (108 mph) to rest over a distance of 66 cm (26 inches) after his throttle got stuck wide open and he hit a wall.

Indy Car driver Kenny Bräck crashed on lap 188 of the 2003 race at Texas Motor Speedway. Bräck and Tomas Scheckter touched wheels, sending Bräck into the air at 200+ mph, hitting a steel support beam for the catch fencing. According to Bräck's site his car recorded 214 g.

(also from Wiki)

 

[QuantumPion]

The g-force you experience in a car crash depends mostly on what your body is stopped by. Let's say you are a crash dummy in a car going 200 mph into a brick wall. If your kinetic energy is absorbed by the tension of a seat belt and the expansion of an air bag, the g-force you experience would be A. If your kinetic energy is entirely absorbed by something solid like the steering wheel/column, it would be B with B >> A. If you went flying out the window, the g-force would be < A as a whole but the local damage received on impact with the window/pavement would kill you by other means (e.g. high g-force to the neck).

 

[Train]

hasnt the govt done tests on pilots on extreme acceleration/deceleration back during the space race? Im sure theres some data out there somewhere with what they came up with.

 

[Gibsons]

Originally posted by: Train
hasnt the govt done tests on pilots on extreme acceleration/deceleration back during the space race? Im sure theres some data out there somewhere with what they came up with.

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