Like the question about the car hitting a block foam, except it’s made out of Superballstuff, specially prepared polybutadiene.
So a car going about 100 km/h hits a 20-meter-thick block of Superball material. The block is 5 meters tall and 5 meters wide and braced against a cliff face (as if it matters much in this case). What happens to the car? I know it gets crumpled but how far back is that car going to bounce? Or does the plastic disintegrate with that kind of impact?
superball stuff will spring it back at 99% speed… its elastic, in that the superball stuff is not absorbing much of the cars energy… its all returned back to the car…
The wall of that stuff would weigh far more than the car… the wall is rather firm and the car is just an insect pushing on it…
While its not quite like hitting a brick wall, the car is made to disintegrate in a crash… the wall of superball stuff is flinging back a shower of car debris at 99 km/h…
I used to write software to analyze test crashes at Ford so I know a little something about what happens when a car hits a concrete wall. However, this is quite different. But the wall isn’t going to absorb 100% of the energy and then bounce the car back out. Like Isilder says, a car is going to crumple when it goes from 100-0 KPH very fast. The wall will absorb some energy and bounce the wreckage back, but the car itself absorbs nearly all of the energy through deformation (which ultimately ends up as heat, as energy is wont to do).
It’s impossible to calculate the bounce without a very detailed structural model of the car in question and analysis of the characteristics of the superwall. This sort of thing would be done empirically. But I’m going to guess that the bounce due to the wall will be no more than a couple of feet. You are not going to get a 100-foot bounce.
If instead of a car, you used an object made of solid steel, then I think would get a very impressive bounce indeed, with the object rebounding at almost its initial speed.
Let’s say it was a 1950s Buick. Not quite solid steel, but a lot closer to it than modern cars. Too bad for the passengers there aren’t any seat belts or air bags, though at that speed maybe those don’t help anyway. Sounds like we have a somewhat shorter car bouncing back at close to 100 k/h.
I recall something about Superballs shattering if they’re hit hard enough. The front of a car has a fairly small area also so that’s a lot of concentrated force. Let’s say we put a steel plate in front of the giant block of plastic to spread the impact and we use a tank hot-rodded up to get to 60+mph.
This business of “old cars = land yacht indestructible tanks lol” that gets stated on the Dope needs to end. If your knowledge about cars begins and ends with watching The Dukes of Hazard, you need to avoid responding and confusing the situation.
ETA: Just want to add that I’m agreeing with Telemark.
I don’t disagree with any of this, but I do disagree with its relevance to our superball scenario.
The problem, as mentioned above, is that the crumple zones on a modern car will dissipate most of the energy from the collision, so there’s little left to send the car shooting back. With an older car, though, very little energy is going to be dissipated as the painfully flimsy sheetmetal buckles. So by the time things like the frame and the engine (which basically are just huge chunks of metal) hit the superball there may still be enough energy to create a satisfying bounce back. Or maybe it’ll just bounce the drivetrain right out the back of the car, which might be even better!
What I think you’ll find is that the older cars crumple just fine, except all that crumpling includes the passenger compartment. In low speed crashes the car frame and body will survive better (if not the passengers) but in high speed crashes those old cars are going to crush in a pretty spectacular manner, including the frame.
Yeah, the whole car will eventually crumple (at least it will if you’re not crashing into a giant bouncy ball) but the difference is that the amount of energy dissipated by the front foot or two of the car before the frame and engine block hits is going to be pretty minimal on an old car, whereas on a modern car those first few feet are where most of the critical energy absorption occurs.
Take a look at the overhead view of the Impala vs Impala crash linked upthread. The older car crumpled all over the place, while the newer car contained most of the crumpling in the front. There’s plenty of deformation of the frame and body on the old car, dissipating a similar amount of energy. When the engine block of the old car hits our giant superball it’s going to just get pushed through the passenger compartment - not rebound.
The top view of that crash seems to be illustrating exactly what I’m saying. If you go to 1:20, during the first few “seconds” of the collision the '09 Impala plows through the front quarter of the '59 Impala like it’s not even there. There’s almost no energy dissipation occurring there. It’s only when it hits the corner of the X-frame just ahead of the passenger compartment that the '59 Impala starts putting up any resistance and the whole car starts crunching.
In that case, by the time solid parts (the frame only since the offset collision misses the engine) of the '59 Impala hit the '09 Impala, the already crumpled-up newer car is physically similar to a brick wall. If it were instead a bouncy ball, it’s possible those solid parts might bounce off and send the car flying back as a semi-cohesive chunk instead of crumpling it. Or, yeah, maybe the engine and frame break loose from the body and get bounced back while the body gets crumpled. Either way it should be pretty spectacular!
And… what happens if you put a Superball in a microwave. Probably nothing interesting but it may have been a good thing there weren’t microwave ovens around when I was a kid.