Fluid mechanics problem

Hi, I have a fluids problem.

A design contest features a sumbarine that will travel at a steady speed of Vsub=1m/s om 15degC of water.
The sub is powered by a water jet. This jet is created by drawing water from an inlet of diameter 25mm, passing this watter through a pump and then accelerating the water through a nozzle of diameter 5mm to a speed of Vjet.
The hydrodynamice drag force can be calculated using F=CdAp(density*(Vsub^2)/2) where the Cd=0.3 and Ap=0.28m^2.
Specify an acceptable value of Vjet.

Please help.
Thanks

Just balance forces. THrust generated by the jet = mass flow times change in velocity. THe inlet and outlet velocities are linked by mass flow in = mass flow out and with density constant the only unknown when you balance will be the exit velocity of the jet. Mass flow = density x area of inlet x inlet velocity. (ie replace inlet velocity in the rate of momentum equation at the start by exit velocity x exit area / inlet area.

Thank you.
How about the hydrostatic equation?
Also i do not know the velocity of the mass going into the jet.

Don't need the hydrostatic equation

Anytime you see the inlet velocity in a formula replace it by exit velocity * (exit area) / (inlet area)

I got 86.6.
you got it right.
when you say thrust = mass flow x change in velocity, what did you use as change in velocity?
Sorry just tryong to get my head around it.
Thanks

Change in velocity = Vjet - Vinlet and again,
replace Vinlet by Vjet*(A-outlet/A-inlet) (You can quickly get this by realising that the by continuity the mass flow in = mass flow out)

As density of the water is constant then A1V1 = A2V2 (1- inlet, 2 - outlet)

If I remember correctly the drag force on the sub worked out to be about 42N
On the other side, the thrust worked out to be something like 0.0189 Vjet^2

Change in velocity = Vjet - Vinlet and again,
replace Vinlet by Vjet*(A-outlet/A-inlet) (You can quickly get this by realising that the by continuity the mass flow in = mass flow out)

As density of the water is constant then A1V1 = A2V2 (1- inlet, 2 - outlet)

If I remember correctly the drag force on the sub worked out to be about 42N
On the other side, the thrust worked out to be something like 0.0189 Vjet^2