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O cada are V= 300 L si avem apa rece cu t1 = 12Ā°C si apa calda cu t2= 80Ā°C . Pentru a face o baie trebuie ca Q = 40Ā°C . Ce volum de apa rece si ce volum de apa calda trebuiesc amestecate ?

Răspuns :

c=4185 J/kgK

V=300 l=0,3 mĀ³

Ļ=1000 kg/mĀ³

Qced=mā‚‚c(tā‚‚-Q)

Qprim=mā‚c(Q-tā‚)

Qprim=Qced<=>mā‚‚c(tā‚‚-Q)=mā‚c(Q-tā‚) |:c=>mā‚‚(80-40)=mā‚(40-12)<=>40mā‚‚=28mā‚|:40=>mā‚‚=0,7mā‚

Ļ=m/V=>m=ĻV=1000*0,3=300 kg

m=mā‚+mā‚‚=mā‚+0,7mā‚=1,7mā‚=>mā‚=m/1,7=300/1,7=176,46 kg

mā‚‚=0,7mā‚=0,7*176,46=123,54 kg

Vā‚=mā‚/Ļ=176,46/1000=0,17646 mĀ³=176,46 l->apa rece

Vā‚‚=mā‚‚/Ļ=123,54/1000=0,12354 mĀ³=123,54 l->apa calda