In two calorimeters we poured 200 g of water each- at temperatures of `+30^(@)` C and `+40^(@)` C. From the "hot" calorimeter 50 g of water, is poured into "cold" calorimeter and stirred. Then, from "cold" calorimeter 50 g of water is poured in "hot" and again stirred. How many times do you have to pour the same portion of water back and forth so that the temperature difference between water in the calorimeters becomes less than `3^(@)` C? Heat loss during the transfer and heat capacity of calorimeters is neglected.

Answer

`5`

Explanation

`200xxSxx30+50xxSxx40=250xxSxxT_(1) T_(1)=32^(@)`
`32xxSxx50+150xxSxx40=200xxSxxT_(2)T_(2)=38^(@)`
`200xxSxx32+50xxSxx38=250xxSxxT_(3) T_(3)=33.2^(@)`
`33.2xxSxx50+150xxSxx38=200xxSxxT_(4) T_(4)=36.8^(@)`
`36.8xxSxx50+200xxSxx33.2=250xxSxxT_(5) T_(5)=33.92^(@)`