*해설

<문제 해설>
P[kW] = γ x h x Q = 60[kW] = 9.806[N/m^3] x h x 0.5[m^3/s]
h[m] = 12.23740567 = f x l x u^2 / 2gd
f = 12.23740567 x 2gd / (300 x 3.978873577^2)
∴ u[m/s] = Q / A = 0.5 / (π/4 x 0.4^2) = 3.978873577

D=0.4 Q=0.5 L=300 P[KW]=60

P=rQH/1000 > 9800*0.5*H/1000 > H=12.24
V(유속) = Q/A > 0.5/(3.14/4*0.4^2) = 3.98
H=fLV^2/2gD > 12.24 = f*300*3.98^2/2*9.8*0.4
f=0.0201