# Can a thrown egg chip (or break) a car windshield?

Is it possible to throw an egg with such speed that a car windshield will chip (just like with stone chips?)

I have searched around for existing research in the area and have found that the impact resistance of an regular hen egg seem to be less than 50 N, which in comparison with all the other forces seem to be rather small and unimportant. Therefore I guess that the question is wether a body of liquid with the properties of raw egg can impact with such force that the window will chip.

I modeled an egg as a cylinder with the cross-area of the widest part of a normal egg (around 40-50 mm) but the problem is that during the impact the area of the egg will most likely increase, and smear out. I assume this has a big impact in wether a chip will occur or not.

My gut instinct is that it is rather unlikely that an egg can damage a windshield, but perhaps, given sufficient throwing speed and, or, car speed, perhaps it is possible.

• Chip? No, you need hard materials to cause a chip (rubber ball doesn't do it either). Damage? Yes, almost anything can damage a windshield if thrown at high enough velocity. – Jim Feb 23 '15 at 22:04
• I have seen paint chipped by thrown raw eggs. A lot depends on exactly which part of the egg hits the windshield. I believe the shell is much harder/stronger on the narrow end, both due to the shape and because the shell is thicker there. – Hot Licks Feb 23 '15 at 22:36
• @JimdalftheGrey: Well, I'm not sure if I use the terminology correctly, but it seems that if you shoot a small rubber ball (like a air soft gun but rubber perhaps) really hard you would be able to get a pattern like this: alertglass.ca/ESW/Images/Chipped_Sheild_1.jpg. But I guess my question is more regarding what I need to know about the egg / general physics to deeper understand the problem. How do I think about the egg smearing out during the impact moments? This will surely reduce the impact pressure greatly? – Filip Nilsson Feb 23 '15 at 23:14
• Ah, you're talking about an impact crater that doesn't penetrate. I don't know for sure that an egg couldn't make a larger version of that, sounds like an expensive test too. – Jim Feb 23 '15 at 23:18

but perhaps, given sufficient throwing speed

If you throw your egg too fast, the force due air resistance

$$F = \frac{cW\cdot A\cdot \rho\cdot v^2}{2}$$

will exceed the 50 Newton you mentioned before and the egg will break.

and, or, car speed, perhaps it is possible

If the car speed is fast enough the glass will of course break, since even single atoms can have a huge impact if only the kinetic energy is high enough (which it is even for a single particle if the relative speed approaches the speed of light).

So the windshield would even break due air resistance if the speed of the car was too high. Real cars of course do not go that fast, but in principle it just depends on the velocity. I also suspect that car manufacturers test their windshields to withstand hits by small birds and stones with twice the maximum velocity of the car, so in real life the glass won't break because of an egg.

• Hopefully they remember to thaw out their small birds before testing! – tpg2114 Feb 24 '15 at 1:55
• @tpg2114 - Nah, the guys at Wright-Pat assured me that the chickens were thawed by the time they hit the windshield. – Hot Licks Feb 25 '15 at 0:29

Yes. Someone trying to drop an egg from an overpass through my open moonroof hit my windshield with it instead. The windshield cracked all over like a spider's web with the epicenter being at the point of impact. The height from which it was dropped was about that of a third-floor window, my speed 5-10 mph.

• Well, strictly speaking, it is an answer, but it's a fairly useless one as it doesn't explain any of the underlying physics. (The fact that this constitutes an answer also indicates that the question is bad.) – David Z Sep 11 '16 at 8:27