Calculating Jet Engine Thrust: How to Use Newton's Second Law

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SUMMARY

The discussion focuses on calculating the thrust of a jet engine using Newton's Second Law. A specific example is provided where the engine takes in 20 kg of air per second at 100 m/s and ejects it at 500 m/s. The correct approach to calculate thrust involves understanding that thrust is a force derived from the rate of change of momentum, not merely velocity. The equation for thrust is clarified as force = rate of change of momentum, emphasizing the importance of momentum in this calculation.

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  • Understanding of Newton's Second Law of Motion
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Homework Statement


A jet engine gets it thrust by taking in air, heating and compressing it, and then ejecting it at a high speed. IF a particular engine takes in 20 k/g of air per second at 100 m/s and ejects it at 500 m/s calculate the thrust of the engine.
chriss #getmoney: thrust of the engine would be v right?

Homework Equations



i believe that the equation is Mv1 + Mv2 = V(Mv1+Mv2) and that the thrust = V .



The Attempt at a Solution

 
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Thrust is a force rather than velocity.

Hint: Try using Newton's Second Law.

Edit: The equation that you have written doesn't make sense, it simplifies to V=1 for all M and v.
 
Last edited:
Welcome to PF!

chrishere? said:
A jet engine gets it thrust by taking in air, heating and compressing it, and then ejecting it at a high speed. IF a particular engine takes in 20 k/g of air per second at 100 m/s and ejects it at 500 m/s calculate the thrust of the engine.
chriss #getmoney: thrust of the engine would be v right?
…
i believe that the equation is Mv1 + Mv2 = V(Mv1+Mv2) and that the thrust = V .

Hi chrishere?! Welcome to PF! :smile:

Thrust is a force, so use Newton's second law in the form force = rate of change of momentum.

How much momentum is being ejected? :wink:
 

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