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- Thread starter waverider
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Newton's law is actually that force is the rate of change of momentum with time,

[tex]F = \dfrac{d(mv)}{dt}.[/tex]

Therefore,

[tex] F = m\dfrac{dv}{dt} + v\dfrac{dm}{dt}.[/tex]

So, if you have a constant velocity, then yes, force can be simply the rate of change of mass times velocity.

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Nidum

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No dynamic force is generated until something happens to accelerate or de-accelerate the flow .

This can be a change in cross sectional area of pipe or a change of flow direction as in a turbine .

Usually better to think of pressures rather than forces when dealing with fluids .

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Cool, thanks

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It would be the force experienced by, say a plate that goes sprayed by that water stream if all of the water from that stream was then deflected sideways when it hits the plate, for example.

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Thanks, a real life example makes it easier to visualizeIt would be the force experienced by, say a plate that goes sprayed by that water stream if all of the water from that stream was then deflected sideways when it hits the plate, for example.

I wounder if F=m(dot).v could be applied to a spray can that is spraying gas at the rate of m(dot) and gas velocity v, would the nozzle experience a force, (disregarding the air pressure and friction) ?

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