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SOS!!extremely urgent matter!!!
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pls solve d folowing question 4me,thnx.
1)ths golden gate bridge in san francisco has a main span of length 1.28km.imagine tat a taut steel wire wit this length n a cross-sectional area of 4.00X10pov(-6)
is laid on d bridge deck wit its ends attached to d towers of d bridge,on a summer day wen d temperature of d wire is 35.0 celcius.
(a)wen winter arrives,d towers stay d same distance apart on d bridge deck keeps d same shape as its expansion joints open.wen d temperature drops to -10 celcius,wats
d tension of d wire?take young's modulus for steel to be 20.0X10pov(10).
(b)permanent deformation occurs if d stress in d steel exceeds its elastic limit of 3.00X10pov(8).at wats temperature would this happen?
(c)hw would ans to (a) n (b) change if golden gate bridge were twice as long?
2)d mass of a hot-air ballon n its cargo is 200kg.d air outside is at 10.0celcius n 101kpa.d volume of d ballon is 400.to wat temperature muz d air in d balon be heated
b4 d balon ll lift off?assume d air density at 10.0celcius is 1.25
3)a liquid has a density A.
(a)show tat d fractional change in density for a change in temperature dT is (delta A)/A=-B*detla T.wat does d -ve sign signify?
(b)fresh water has a max density of 1.00g/cm3 at 4.0 celcius.at 10.0celcius,its density is 0.9997 g/cm3.wats B for water over this temperature interval?
4)a box wit a total surface area of 1.20 n a wall thicness of 4.0 is made of an insulting material.a 10.0-W electric heater inside d box maintain d inside temperature at
15.0celcius above d outside temperature.find d thermal conductivity,k of d insulting material.
5)a pond of water at 0celcius is covered wit layer of ice 4.0cm thick.if d air temperature says constant at -10.0celcius,hw long does it take for d ice thickness to increase
to 8.0cm?utilise d equetion dQ/dx=kA*delta T/x,wher dQ=LPAdx wit L is d latent heat of fusion n P is d density of ice.
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[ Last edited by Asurahyde on 6-12-2004 at 05:54 PM ] |
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发表于 5-12-2004 07:23 PM
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