我想問兩個Physics問題呀

(1)(a)
Energy for water to gain hear per second
= Energy of the engine to lose heat per second
= mCΔT
= 1x4200x(95-15)
= 336000J/s
(b) I think the mass of engine = 200kg (not 200g)
Let t be the time for heat up the engine
Energy produce by the engine
= mCΔT
= 200x450x(200-15)
= 16650000J
= energy to heat the water (Assume the cooling system doesn't fail)
= 1(t)(4200)(200-15)
= 777000t J
t = 21.54s
(2)
Let C be the specific heat capacity of iron
Ta & Tb be the temperature change of iron A and that of B
Let Ma and Mb be the mass of iron A and iron B respectively
Let power of C & D be Pc & Pd
Let t be the time to heat the iron blocks
Ta/Tb = 4/3 => Tb = 3Ta/4 -----(1)
Pc/Pd = 3/4 => Pd = 4Pc/3 -----(2)
Energy gain by the block A, Pc (t) = Ma C Ta ------(3)
Energy gain by the block B, Pd (t) = Mb C Tb -----(4)
sub eq(1) and eq(2) into eq(4):
4Pc(t)/3 = Mb C (3Ta/4)
Pc (t) = 9(Mb C Ta) /16 -------(5)
eq(3)/eq(5) :
1 = Ma/(9Mb/16)
Ma/Mb = 9/16
Ma : Mb = 9 : 16
The mass ratio of A and B = 9 : 16 respectively

2008-10-05 13:56:11 補充：
Revised for part 1(b)
Let t be the time for heat up the engine
Energy produce by the engine
= mCΔT
= 200x450x(200-15)
= 16650000J
energy for water to cool engine per second
= 1(t)(4200)(95-15)t
= 336000t J
energy for water to cool engine per second = energy produce by the engine
336000t=1665000
t = 34.7s