Concept:
Vr = relative velocity of the jet with respect to the plate
● When the plate is moving (u) in the direction of the jet (V) i.e. away from the jet:
Vr = V - U
● When the plate is moving (U) in the opposite direction of the jet (V) i.e. towards the jet:
Vr = V + U
Force exerted by the jet on the plate in the direction normal to the plate:
Fn=m[V1n−V2n]=ρAVr[Vrsinθ−0]
Fn=ρAVr2sinθ Force exerted by the jet on the plate in the direction of the jet (
Fx ) and is perpendicular to the direction of flow (
Fy )
Fx =Fnsinθ =ρAVr2sin2θ Fy =Fncosθ =ρAVr2sinθcosθ Calculation: Given, velocity of jet = 20 m/s
Angle between jet and plate = 60° and area of cross-section of jet = 0.01
m2 Flate plate is stationary, Then
Relative velocity of the jet with respect to the plate(
Vr ) = 20 - 0 = 20 m/s
The perpendicular force to flow exerted by a jet on a stationary inclined flat plate, Fy = ρAVr2sinθcosθ Fy = 1000×0.01×202×sin60×cos60 Fy = 1732.05 N.