Brain Teasers
Not So Great Invention #2
Not willing to give up after a failed attempt to invent a better windshield ice scraper, a would-be inventor decided that heated windshield washer fluid was the way to go. It would melt the ice with a very hot cleaning solution, thereby eliminating the need for scraping the ice off the front windshield. However, this invention proved a failure as well. Passing all tests done to insure it worked, it did indeed remove the ice effortlessly in record time. It even sold well initially, but was recalled for safety reasons.
Why?
Why?
Hint
What happens to glass if heated too fast?Answer
Windshields can withstand a fair bit of expansion and contraction from cold & heat. Yet in cases of extreme cold, the hot fluid caused the glass windshields to crack. The car that was used for testing was sitting still at -15 degrees Celsius but a car driving at 120 km /h creates a wind chill of -33 deg. In some northern areas temperatures of -30 are not uncommon, giving a wind chill of -56 deg., far too cold to be spraying hot liquid on a windshield.Hide Hint Show Hint Hide Answer Show Answer
What Next?
View a Similar Brain Teaser...
If you become a registered user you can vote on this brain teaser, keep track of which ones you have seen, and even make your own.
Solve a Puzzle
Comments
Just a question, because I'm unsure of something: Does windchill affect inanimate objects? I think I've been told that the wind makes it FEEL that cold, but isn't it still just the regular temperature? For example: If it's 10 degrees here and 10 degrees 5 miles away, isn't the wind still just 10 degrees even if I'm driving through it? I'm really not sure...
That a good question i'm not really sure. I do know it does increase the rate at which things cool down but I'm not sure if the end temp is affected. I'll have to look in to it. In any case it seems it was cold enough to crack the windshields .
Wind chill does not affect inanimate objects. It can never be colder than the real air temperature. The wind produced by a moving car will cause heat to be disappated more quickly than when standing still. The wind chill temperature is not what will cause the windshield to crack. However, the speed at which the temperature drops from the hot liquid to the air temperature might very well cause a break.
Cnmne's right. The speed of the car doesn't make the temperature lower, it just makes it get to the same final temperature faster. Also, glass doesn't crack because it's too hot or too cold. It cracks because part of it is changing temperature faster than another part. This creates stress in the glass (because half of it is trying to expand or contract and the other half isn't), causing the crack. The key to this teaser is the SPEED at which the glass changes temperature, not the temperature itself.
WELL there you have it thanks guys for the technical explanation,
i like these not so great inventions!
nice puzzle od!!!
bobbrt is right about the differential heating that causes glass to crack. that is the reason why very hot liquids are not poured fast into glass tumblers.
bobbrt is right about the differential heating that causes glass to crack. that is the reason why very hot liquids are not poured fast into glass tumblers.
Boy do I feel dumb. You guys are all to technical. It's amazing what you can learn while having fun!!!
Many, many years ago I just had to test out the do not put a hot piece of glass into (or pour into) cold water. Guess what?! I'll never use that measuring pitcher again!!! It works the same as your teaser and the cold windshield and hot cleaner. CRACK....Enjoyed this one even if it did remind me of my once favorite pitcher!
Seems like the tests that were done to see if it worked weren't all that great...
As good as the first one.
I knew the glass would crack but now I know why it cracks. Thanks for the info. Good teaser.
To post a comment, please create an account and sign in.
Follow Braingle!