variable (+2151)
2.
[tex]\[\begin{array}{l}
N = 81kW = 81000W\\
\eta = 25\% \\
q = 4,2 \cdot {10^7}J/kg\\
t = 1h = 3600s
\end{array}\][/tex]
==========================
[tex]\[\begin{array}{l}
A = Nt = 81000W \cdot 3600s \approx 2,9 \cdot {10^8}J\\
Q = A/\eta = \frac{{2,9 \cdot {{10}^8}J}}{{25}} \approx 1,17 \cdot {10^7}J
\end{array}\][/tex]
[tex]\[m = Q/q = \frac{{1,17 \cdot {{10}^7}J}}{{4,2 \cdot {{10}^7}J/kg}} \approx 0,277kg\][/tex]
Ats. turėtų būt 27,77kg
3.
[tex]\[\begin{array}{l}
v = 27km/h = 7,5m/s\\
m = 400kg\\
\eta = 30\% \\
q = 4,2 \cdot {10^7}J/kg
\end{array}\][/tex]
[tex]\[\begin{array}{l}
N = \frac{A}{t} = \frac{{5,04 \cdot {{10}^{11}}J}}{{3600s}} = 1,4 \cdot {10^8}W\\
F = \frac{N}{v} = \frac{{1,4 \cdot {{10}^8}W}}{{7,5m/s}} = 1,87 \cdot {10^7}N = 18700kN
\end{array}\][/tex]
ats. turėtų būt 186,7kN
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