A man is drilling an iron block of 2.5 kg.The power of drill is 2500W.Suppose 60% of the power has been lost as heat and increases the temp. of the iron block.The S.H.C of iron is 470
(a)Find the temp. rise of block in 1 min.
ans:76.6
(b)If water is dripping into the hole at steady rate of 20g s^-1,find the temp. rise of block in 1 min.
ans:14.5
(c)Find the maximum temp. increase of the block if water is dripping into the hole at rate stated in (b).
ans:17.9
calculation-heat
2007-01-13 2:15 am
回答 (1)
2007-01-13 6:15 am
✔ 最佳答案
(c) The heat gain by the dripping water in 1 sec= (20/1000)x 4200 x T
where T is the rise in temperature of the water, and 4200 J/kg-K is the specific heat capacity of water
Heat generated by the drill = 2500 x 0.6 J/s
The temperature of the block will become steady when the heat generated is all taken away by the dripping water.
i.e. 2500x0.6 = (20/1000)x 4200 x T
solving for T gets T = 17.9 deg.C
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