- #1
TheTank
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Homework Statement
A model car weighs 17N and is accelerated from rest by a 1cm diameter water jet moving at u=75m/s. Neglect all friction, find the velocity of the car after is has moved 1m.
Homework Equations
Reynold's
[tex]\sum{\vec{F}}=\int_{CS}{\rho\vec{V}(\vec{V_{rel}}\cdot \vec{n})dA}[/tex]
The Attempt at a Solution
[tex]\sum{F}=\rho A (u-v)(u+v) + \rho A(u-v)(u-v)[/tex] => [tex]\sum{F}=-2A\rho uv[/tex]
[tex]E_{k}=0.5mv^2 =\int^1_0 F \cdot ds=\frac{2\pi D^2 \rho uv \cdot s}{4}[/tex] => [tex] v=\frac{\rho u D^2 \pi s}{m}[/tex]
I get the wrong answere when i put in the numbers.. v should be 25m/s