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Homework Statement:
 Hey guys, my problem is in the linked task the first letter a). I tried to calculate this problem since 2 hours and dont get on the solution. Please excuse my english, its not my native language.
Relevant Equations:

g*h1+p1/rho+(v1^2)/2 = g*h2+p2/rho + v2^2/2 + dpl
dpl = Pressure loss
dpl = 1/2 * rho * v1^2 * loss coefficient
So when the velocity of v1 and v2 is 0 (because the tanks are much bigger), the bernoulli equation to dh is dh = (dpdpl)/(rho*g)
with dp = Phyd / V = 1000W / 0.01m³/s = 10^5 Pa and rho = 1000 kg/m³
So Im getting first without the pressure loss on the orifice dh = 10^5 Pa / (1000 kg/m³ * 9,81 m/s²) = 10.2m
So the loss coefficient for a standard orifice and for D2/D1 = 0.6 is 2 (according of the supplement what our prof gave us)
v1 = V / (r2²*pi) = 1.27 m/s
dpl = 1/2 * 1000 kg/m³ * (1.27 m/s)² * 2 = 1613 Pa
Now Im gettin dh with the pressure loss
dh = (10^5 Pa  1613 Pa) / (1000 kg/m³ * 9,81 m/s² ) = 10.03m
Still dont get to the 6.8m. And I dont know what up, so the pressure loss should be much much bigger than these 1613 Pa.
Im very thankfull for every help.
with dp = Phyd / V = 1000W / 0.01m³/s = 10^5 Pa and rho = 1000 kg/m³
So Im getting first without the pressure loss on the orifice dh = 10^5 Pa / (1000 kg/m³ * 9,81 m/s²) = 10.2m
So the loss coefficient for a standard orifice and for D2/D1 = 0.6 is 2 (according of the supplement what our prof gave us)
v1 = V / (r2²*pi) = 1.27 m/s
dpl = 1/2 * 1000 kg/m³ * (1.27 m/s)² * 2 = 1613 Pa
Now Im gettin dh with the pressure loss
dh = (10^5 Pa  1613 Pa) / (1000 kg/m³ * 9,81 m/s² ) = 10.03m
Still dont get to the 6.8m. And I dont know what up, so the pressure loss should be much much bigger than these 1613 Pa.
Im very thankfull for every help.
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