Determine the power of the jet engine of an airplane

[Fisicks]

Homework Statement

The jet engine of an airplane takes in 130 kg of air per second, which is burned with 4.3 kg of fuel per second. The burned gases leave the plane at a speed of 600 m/s (relative to the plane). If the plane is traveling 260 m/s, determine the power (hp) delivered.

Homework Equations

P=Fv
M(DV/DT)=F_ext + v_rel(DM/DT)

The Attempt at a Solution

dv/dt=0 so F=v_rel(DM/DT)
Thus W=v^2(DM/DT)=(600^2)(4.3) but this is incorrect and I do see where I am wrong.

 

[tiny-tim]

Hi Fisicks!

You've used mdv/dt, which obviously doesn't work if m is not constant

(and dv/dt = 0, which I don't really understand)

start again, using the full version of good ol' Newton's second law …

force = rate of change of momentum ​