A certain amount of ice is supplied heat at a constant rate for 7 minutes. For the first one minute the temperature rises uniformly with time. Then, it remains constant for the next 4 minute and again the temperature rises at uniform rate for the last two minutes. Calculate the final temperature at the end of seven minutes. (Given, L of ice `= 336 xx (10^3) J//kg` and specific heat of water `= 4200 J//kg-K`).

A certain amount of ice is supplied heat at a constant rate for 7 minu

1.	A certain amount of ice is supplied heat at a constant rate for 7 minutes. For the first one minute the temperature rises uniformly with time. Then, it remains constant for the next 4 minute and again the temperature rises at uniform rate for the last two minutes. Calculate the final temperature at the end of seven minutes. (Given, L of ice `= 336 xx (10^3) J//kg` and specific heat of water `= 4200 J//kg-K`).
Answer» Correct Answer - C::D Let heat is supplied at a constant rate of `(alpha) J/(min)`. In 4 minutes, (when temperature remains constant) ice will be melting. `:. } mL = (4) alpha` `:. alpha/m = L/4 = (336 xx (10^3))/4` `=84 xx (10^3) J//min-kg` Now in last two minutes, `Q = msDeltatheta` `:. (alpha)(2) = (m)(4200)(theta - 0^@C)` Substituting the value of `alpha/m` we get, `theta = 40^@C` .

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