Calculating Turbojet Thrust with Exhaust Deflection

[Freyster98]

Homework Statement

The idling engines of a landing turbojet produce forward thrust when operating in a normal manner, but they can produce reverse thrust if the jet is properly deflected. Suppose that while the aircraft rolls down the runway at 150 km/h, the idling engine consumes air at 50 kg/s and produce an exhaust velocity of 150 m/s.

a. What is the forward thrust of the engine?
b. What are the magnitude and direction (i.e. forward or reverse) if the exhaust is deflected 90∘without affecting the mass flow?
c. What is the magnitude and direction of the thrust (i.e. forward or reverse) after the plane has come to a stop, with 90∘exhaust deflection and airflow of 40kg/s?

Homework Equations

The Attempt at a Solution

Part a was easy, but I'm confused about parts b and c. If the exhaust is deflected 90 degrees, wouldn't the thrust be directed up or down, depending on the direction of the rotation? If so, the "forward or reverse" statement would be irrelevant, right?

 

[Freyster98]

Sorry guys, I misinterpreted the question. I'd delete this but don't know how.