Physical 問題2(+20)

1a)
The boiling temperature = 100oC

Energy that the water gain when it just reaches boiling
= m c ΔT
= 0.5 x 4200 x (100 - 20)
= 168000 J


1b)
Assume that there is no heat loss to surroundings.

Estimated heating power of the oven
= E/t
= 168000/(7 x 60)
= 400 W

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2)
(a) and (b) are correct.

(a) is correct.
Most of the vehicles use water as a coolant.

(b) is correct.
Our body contains mainly water. The change in temperature of our body is small due to the high specific heat capacity of water.

(c) is incorrect.
Due to the high specific heat capacity of water, temperature of sea water rises and falls more slowly than that of the land.

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3)
(b) is correct.

(a) is incorrect
The temperature of the body increases, but there is no sufficient information to determine the final temperature. The body would become slightly warmer, or become very hot.

(b) is correct.
Temperature of the body is a function of average kinetic energy of the particles in the body.

(c) is incorrect.
The potential energy of the body remains unchanged.

(d) is incorrect.
The specific heat capacity of the body remains unchanged.
=

1:0.5*4200*(100-20)/(7*60)
=400W
2:a+b
3:b

2008-12-12 18:50:06 補充：
1:0.5*4200*(100-20)
=168000J

2008-12-12 18:51:14 補充：
1a:0.5*4200*(100-20)
=168000J
1b:0.5*4200*(100-20)/(7*60)
=400W