Which of the following statements concerning the action of a rocket engine is/are correct?
I. The momentum of the exhaust gases is equal to the momentum of the rocket
II. The total momentum change of exhaust gases and the rocket is zero
III. The chemical energy of the fuel is less than the kinetic energy converted
A. I only
B. II only
C. I and II only
D. II and III only
phy mc - momentum
2007-04-25 3:20 am
回答 (1)
2007-04-25 3:41 am
✔ 最佳答案
一個closed system入面既動量應要conserve (law of conservation of momentum)换句話講,closed system入面所有momentum相加要互相抵消,所以一啱exhaust gas向下噴,有一向下的momentum,而火前會得到一個magnitude相同,但方向向上既momentum,所以火前先會向上升,二啱.
根據能量守恆定律
燃料內的化學能少過火箭的動能是不可能的
所以答案係c
2007-04-24 19:43:43 補充：
修正版：一個closed system入面既動量應要conserve (law of conservation of momentum)换句話講,closed system入面所有momentum相加要互相抵消,所以二啱exhaust gas向下噴,有一向下的momentum,而火前會得到一個magnitude相同,但方向向上既momentum,（都係law of conservation of momentum）所以火前先會向上升,一啱.根據能量守恆定律燃料內的化學能少過火箭的動能是不可能的所以答案係c
參考: Phy reference book
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