Can you brake hard enough to go through the windshield?

I was just flipping channels and caught the opening of Tango and Cash where two guys in a transfer truck slam on the brakes and fly through the windshield and it dawned on me that I’ve seen this in movies before and never believed it could happen. Obviously, a transfer truck is unlikely to stop that fast, but can you do it in a car?

I’ve had a ride in a Porsche race car that had amazing brakes and may have been capable of sending me flying so let’s say it has to be an average car sold to the public. This can include sports cars like the Corvette and Porsche, but no million dollar exotics, and let’s imagine the vehicle doesn’t have a windshield to hold you in.

Hollywood and their idea of hvac systems? Love the fans pullling from out side and exhausting to out side. Or stopping a large AC motor using a bar, then having it restart and snot sjhort or trip out.

Once your foot leaves the brake pedal, which it must do if you are to go through the windshield, both the car and you stop decelerating.

What about a passenger? I guess my question should be: “With the cars on the road today, are any capable of decelerating fast enough to eject a person?”

Are you talking about the prison break scene? I didn’t watch the rest of the movie but I remember that. Too funny.

It would be possible to design a car that could but the reality of it is that the mass of a normal car prevents this from happening. If you made a vehicle that weighed a couple of hundred pounds and used massive sticky tires then the answer is yes. Keep in mind that a windshield has a piece of plasic film in the center of the glass that is designed to stop objects from passing through. You can certainly plaster a person into the window if they’re not wearing seatbelts but actually going through it is not going to happen from braking.

Interesting. On the face of it I could believe it. Once, while riding around in my parents’ old 1987-ish Subaru Legacy (4 cylinder, front wheel drive sedan), I slammed on the brakes with a friend of mine riding in the center of the back seat without a seat belt. He flew forward between the two front seats, narrowly missing hitting his head on the dashboard. This was not even on the highway, I was going 40 MPH tops between red lights on a two-lane stretch of local road, and he wasn’t a big heavy guy either (probably 5’ 8" and 150 lbs. or so).

So… Someone heavy riding in the passenger seat of a really fast sports car without a seat belt, and with very good brakes/tires, could certainly hit the windshield awfully hard. Whether it would be hard enough to go through the windshield is not something I know how to calculate though.

Yes, that was funny.

That happens quite frequently. Child standing up in the front seat, parent brakes the car, and child comes crashing into the windshield. Don’t know of any situations where the child broke through and was thrown from the car.

A car’s deceleration using the brakes (or any other kind of acceleration on a level road) is limited by the friction between the tires and the road: The maximum acceleration possible is g times the coefficient of friction. Typical coefficients of friction are usually somewhere in the vicinity of 1 or less, so you’re not going to get accelerations much greater than 1g.

Without a seat belt, meanwhile, a passenger is going to be held in his seat by friction, as well. If the friction between the passenger’s butt and the seat is greater than that between the road and the tires, he’ll stay put, and if it’s less, he’ll slide forward in his seat. If nothing else stops him, eventually his body will hit the dashboard, and the upper portion of his body will fold around it and hit the windshield. Given that tires are specifically designed for high friction, and butts and car seats aren’t, I’m going to guess that the butt-seat friction is less, maybe about 0.5 . So for a completely limp rag-doll passenger, it would be possible to hit the windshield.

Of course, real passengers aren’t completely limp rag-dolls, either. A real passenger would probably have enough reaction time to get his arms in front of him to brace against the dashboard, and even if he didn’t, his body won’t fold around the dashboard completely effortlessly, either. So for a real passenger, I think the chance of hitting the windshield at all is pretty small, and even if one did, it’d be unlikely to have enough energy left to break through it.

I would think that braking hard in an attempt to propel oneself through the windshield would be doomed to failure, since you’d reflexively flinch back and just wind up mooshing yourself against it instead. What you need is the element of surprise.

Like that of your front seat passengers who aren’t expecting a violent braking maneuver.

Maybe not braking, but the amount of force a car has when it is rapidly decelerating (like it hits a tree) is extremely great. Even an extremely strong individual won’t be able to brace themselves against the dash or steering wheel to stop themselves from slamming into the windshield and probably going through it.

The questions is whether the deceleration from just braking is strong enough. When I was very young, a friend of my parents were driving their station wagon when they suddenly braked. I was in the back seat wearing a seatbelt (my parents insisted). The friends children were not. There were three of them. One was sitting next to me, one was riding shotgun, and the last was in the back of the wagon sitting on the floor.

The child in back was tossed into the seat next to me and hit my head. The child next to me was tossed into the front seat and the one riding shotgun fell out the passenger window. I can’t remember all the damage. I had a concussion from having the kid in back slam into my head. But I believe one of the kids did die later on.

After that, I refused to ride in many of my friends cars because they didn’t have seat belts. (I don’t think they were standard equipment in the back seat until the mid-1960s).

When I was a third grader, I was sitting on the middle bench seat of my family’s Ford van without a seat belt on when my father made an emergency stop at an intersection; I was thrown forward between the front seats and knocked my right front tooth out on the dashboard. I suppose that with a few more mph I would have hit the windshield.

I had that tooth reimplanted, and it lasted until earlier this year. I’m now in the process of getting an implant. Since the accident, I’ve never ridden in a car without having my seat belt on.

No dispute here; I was restricting to the case of deceleration caused by braking.

Someone clearly needs to get Mythbusters on the case. You just know if there’s any possible way they can send Buster flying, they’re going to do it.

That’s very true. People think that by installing bigger brakes on their cars they will brake in shorter distance but they do not realize that even the stock brakes can exert much greater than the required force and the actual weakest link is the tires.

Like you said, normal cars on high performance street tires can do about 1g max. Lightweight cars (like Caterham, Ariel Atom etc) can do about 1.1-1.2g on street tires. Cars with slick, soft compound tires can do ~1.5g and if combined with aerodynamic downforce they can exceed 1.5g

So a typical car (of medium weight, street tires and no aerodynamics) can’t have more than 1g of deceleration consistently. Mercedes Benz has developed an experimental airbag-like device that deploys when a colision is imminent, somewhere between the front of the car and the road surface. This, combined with the normal brakes, can generate up to 2g of braking force.

Actually, the car has nothing to do with it. Say you weigh 200 lbs. That means your momentum is equal to 200 lbs of meat traveling at whatever speed the car was going before it stopped minus the friction force between your ass and the seat. If your car instantly stopped, you’d go flying no matter if it was a pinto or a semi, and you’d have the same momentum either way.

A couple nitpicks - the Atom doesn’t generally come with “Street” tires, unless you count R-compound “street legal” race tires. The normal factory tire is the Yokohama A048 or the Toyo R888.

In an Atom cornering on the track, it is not unusual to exceed 2G, with instantaneous peaks quite a bit higher. I don’t know about when braking, though - the idea is to not have to come to a stop on the track :smiley: and thus I never bothered to look at the accelerometer data for that.

The Atom does out-brake most other cars in the Autocar 0-100-0 test (ugly URL that may or may not keep working here) even without an aero kit.

While it is a lot lighter than other cars and thus easier to stop, the car weight doesn’t change what the passengers feel. A quick stop (or start) in an Atom is something to be savored.

Yes, I own an Atom. More info here.