Is a 60mph car colision with a solid wall the same as 2 cars going 30mph on a headon collision?

Question

2 cars, each going 30= same effect as a collision at 60 to a non moving wall?

Answer 1

The single-car crash has about twice the effect.

In either case, we can assume that all of the kinetic energy of the car or cars will be used to demolish the car or cars. The kinetic energy of a moving mass is given by energy = 1/2 x mass x velocity squared. If the weight of the car is used instead of the mass, it is necessary to divide the result by g, the acceleration due to gravity, 32 ft/sec^2.

For a 4000 lb. car going 60 mph (88 ft/sec), energy = 0.5 x 4000 x 88^2 / 32 = 484,000 ft-lb.

For two 4000 lb. cars each going 30 mph (44 ft/sec), energy = 0.5 x 8000 x 44^2 / 32 = 242,000 ft-lb.

Edit 1
In addition, with one car, all the energy will be expended on one car rather than divided between two cars. The energy per car will be four times as much with only one car absorbing all of the energy.

Since the question is stated as "non-moving wall" and "headon," No consideration has been given to real-world effects of some destruction of the wall and some friction with the road after impact.

Answer 2

At first, you'd think so, but no. The reason is that the "solid wall" isn't going to give at all. So one car hitting a solid wall gets the advantage of the designed in "give" of only its own structure. Two cars hitting head on will both "give" to some degree. You'd be better off in the head-on. Odds are, there'll be a certain amount of deflection left/right at impact, too.

All of this has to do with a concept called (believe it or not) "jerk"... unless you're in the UK, where they will sometimes be found calling this "jolt".

Velocity is speed. A change in velocity is called acceleration. A change in acceleration is, under these circumstances, called "jerk". It's effects are quite amazing. This "delta delta V" really has a great deal to do with the effects of impact. No object can be stopped instantaneously, but the closer you come to this, the greater the destructive result.
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Answer 3

The impact speed is the same, but the results would be much different-- the cars are designed to "give" and the bodies would help absorb some of the impact. Hitting the wall, the car would absorb some, but there would be less "give" from the wall, so the damage would be much more severe

Answer 4

In theory, however, the solid wall in reality is worse. This is because:

- pieces of the cars are likely to fly past the impact
- cars are likely to spin and go past the line of impact.

Answer 5

here's the math

mv + mv

let's assume the mass is 1kg
1kg (30mph) + 1kg (30mph) = 60 Joules

if it were a brick wall it would be

1kg (60mph) + 0kg (0mph) = 60 Joules

Answer 6

Pretty much.

Answer 7

why would you even think that