posted by elisabeth .
thanks again to anyone who can possibly help!!!!! i wish i had a book or notes or something about this kind of stuff :(
The linear expansion coefficient of glass is 9 x 10^-6 (`C)^-1.
An automobile windshield has dimensions of 59 cm by 390 cm. What minimum spacing around the windshield is needed to prevent the windshield from breaking if the temp. changes to 146` F.?
Assume the normal temperature of the glass, when installed, is 66 F, so you want to design for an 80F rise in temperature. That is a 45 C temperature rise. The long dimension of the window will expand most, by an amount
390 cm * 45 C * 9*10^-6 C^-1 = 0.16 cm = 1.6 mm
You should leave a gap of 0.8 mm at each end. The gap at the top and bottom can be less, but might as well be the same.
A body cools from 50 degree celcious to 49 degree celcious in 5 seconds. How long will it take to cool from 40 degree celcious to 39 degree celcious? ( assume temperature of surroundings to be 30 degree celcious and newtons law of cooling is valid)