fomula of forces

Jun 2014
306
0
why the Fx is given by the formula = ρ AV1 ( V1 - V2 cos θ ) , why not = ρ A( V1 - V2 cos θ ) ???
 

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ChipB

PHF Helper
Jun 2010
2,369
294
Morristown, NJ USA
Well for one thing check your units . The formula you gave does not result in force - it has units of Kg/s, not Kg-m/s^2. So that tells you right away that your formula is incorrect. They start by stating that F=m delta V, but that's not quite right - it should be F = delta (mv)/delta t = dm/dt times delta V. The quantity dm/dt is mass flow, or rho AV. The quantity delta(v) is the (V1-V2 cos theta) term.
 
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