Having problems trying to solve part b of this problem.
Rocket Propulsion Elements 8th - Chapter 2
- A jet of fluid hits a stationary flat plate in the manner shown below.
(a) If there is 50 kg of fluid flowing per minute at an absolute velocity of 200 m/sec, what will be the force on the plate?
(b) What will this force be when the plate moves in the direction of flow at u = 50 km/h? Explain the methodology.
Part A just involves plugging in mass flow rate, changing units to seconds, multiplying it by characteristic velocity to get force.
Part B, I have zero idea what's going on. I thought it was a conservation of momentum problem, so I set up the problem as F = dm * v^2, where v is 200-13.8 (13.8 being the change in speed in m/s as the plate moves away). The problem is, I'm getting 155 N, whereas the correct answer is 144 N.