F4 Physics calculating

2009-09-27 6:57 pm

May is going to cook some vegetable. She is choosing between frying vegetable or
cooking it with water. If May fries vegetabke, she will use 20-g olive oil, heat the oil to
about 200 degree celsius from 27 degree celsius, fry vegetable and add a pinch of salt. If she cooks vegetable with water, she will boil 1-kg water and then add 10-g olive oil and a pinch of salt. The output power of her stove is 2000W.
(Given: specific heat capacity of olive oil = 1970 J kg^-1 degree celsius^-1
specific heat capacity of water = 4200 J kg^-1 degree celsius^-1)

If 10000 J is requiered to cook the vegetable, how long will it take for the whole cooking process?

回答 (1)

天同

2009-09-27 8:52 pm

✔ 最佳答案

Heat required to boil 1 kg of water
= 1 x 4200 x (100-27) J = 306 600 J
Heat required to boil 10g of olive oil
= (10/1000) x 1970 x (100-27) J = 1438.1 J
Totoal heat required = (306600 + 1438.1) J = 308 038 J
Time required to boil the water and oil
= 308038/2000 s = 154 s
Time required to cook the vegetable
= 10000/2000 s = 5 s
Hence, total time needed to complete the whole cooking process
= (154 + 5) s = 159 s

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