Anonymous
Anonymous asked in 科學及數學其他 - 科學 · 1 decade ago

momentum 問題...

A jet engine on a test bed takes in 20.0kg of air per second at 100ms-1 and burns 0.8kg of fuel per second. After compression and heating the exhaust gases are ejected at 500ms-1 relative to the aircraft. Calculate the thrust of the engine.

1 Answer

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  • 天同
    Lv 7
    1 decade ago
    Favorite Answer

    Change of momentum of the air in 1 second

    = 20 x (500-100) Ns = 8000 Ns

    Change of momentum of the fuel in 1 second

    = 0.8 x 500 Ns = 400 Ns

    hence, total change of momentum = (8000 + 400) Ns = 8400 Ns

    Thrust = rate of change of momentum = 8400/1 N = 8400 N

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