Lecture - 2 (impact of jets)

Before starting with impact of jets we must learn about forces. Force is nothing but rate of change in linear momentum. When we apply force on a body, than its Momentum will change and this change in momentum will represented by subtraction of initial momentum of body from its final momentum.
Force applied on a body = final momentum of body - initial momentum of body
Let us consider a stationary vertical plate on which a jet is striking. The jet is having diameter 'd'. The mass flow rate of Jet is represented by 'm' kg/s. This simply means that 'm' kilogram of water is coming out of nozzle per second. The jet is striking at the middle of the plate with velocity 'V1' metre per second. After the impact of Jet on the plate, the jet will split equally and flows over the plate. After that the jet will exit the plate from its tip in tangential direction. Now here Jet is striking the plate normally or perpendicularly at point 1 and exit the plate tangentially from the tip of the vertical plate represented by point 2 with velocity 'V2' m/s. If we consider this plate to be frictionless then the entry velocity and exit velocity will be same (V1=V2).

In above figure consider this plate vertical and jet is striking perpendicularly to the plate.
Water jet striking with the force 'Fj ' on stationary plate. Now plate will apply reaction force 'Fp '. This jet force and plate force are equal and opposite action and reaction forces.
Fp = rate of change in linear momentum
     = Final momentum - initial momentum
As we know Fj = -Fp 
∴ Fj = initial momentum - final momentum
       = mV1 - mV2


After this continue to lecture - 3

you guys can check its video explaination also on my you tube channel Mechanical education hub

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