Răspuns:
[tex]\boxed{\boxed{\bf \Delta t = 450\, s }}[/tex]
[tex]\boxed{\boxed{\bf L_{F_f} = 90\, KJ }}[/tex]
Explicație:
[tex]\bf P=\dfrac{L}{\Delta t} =F \cdot v[/tex]
[tex]\bf P=F \cdot v= 40 \, N \cdot 5 \dfrac{m}{s}[/tex]
[tex]\bf P=200 \dfrac{N\cdot m}{s} =200\dfrac{J}{s} =200\, W[/tex]
[tex]\bf P=\dfrac{L}{\Delta t} \implies \Delta t = \dfrac{L}{P} = \dfrac{90\, KJ}{200\,W}[/tex]
[tex]\bf \Delta t = \dfrac{90 000 \, J}{200\dfrac{J}{s} } = 450 \, \dfrac{J}{\dfrac{J}{s} } = 450\, J : \dfrac{J}{s}[/tex]
[tex]\bf \Delta t = 450\, J \cdot \dfrac{s}{J } \implies \boxed{\bf \Delta t=450\, s}[/tex]
[tex]\bf F_{tractiune} = \dfrac{P}{v} =\dfrac{200\,W}{5\dfrac{m}{s} } =200\dfrac{J}{s} : 5\dfrac{m}{s}[/tex]
[tex]\bf F_t = 40 \dfrac{N\cdot m}{s} : \dfrac{m}{s} =40\, N[/tex]
[tex]\bf F_t = F_f \implies \boxed{\bf F_f = 40N }[/tex]
[tex]\bf \implies L_{F_f}=L_F \implies \boxed{\bf L_{F_f} =90\,KJ }[/tex]
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