[tex]dane:\\v_{o} = 0\\m = 400 \ t = 400 \ 000 \ kg\\v = 300\frac{km}{h} = 300\cdot\frac{1000 \ m}{3600 \ s} = \frac{250}{3}\frac{m}{s}\\s = 3 \ km = 3 \ 000 \ m\\szukane:\\F = ?\\\\Rozwiazanie\\\\Z \ II \ zasady \ dynamiki\\\\a = \frac{F}{m} \ \ |\cdot m\\\\F = m\cdot a\\\\ale:\\\\s = v_{sr}\cdot t\\\\v_{sr} = \frac{v_{o}+v}{2} = \frac{1}{2}v\\\\s = \frac{1}{2}vt \ \ |\cdot2\\\\v\cdot t = 2s \ \ |:v\\\\t = \frac{2s}{v} = \frac{2\cdot3000 \ m}{\frac{250}{3}\frac{m}{s}} = 72 \ s[/tex]
[tex]F = m\cdot a\\\\ale \ \ a = \frac{v}{t}\\\\F = m\cdot\frac{v}{t}\\\\F = 400000 \ kg\cdot\frac{\frac{250}{3}\frac{m}{s}}{72 \ s} \approx 462 \ 962,96 \ N\\\\F \approx 462 \ 963 \ N \approx 463\ kN[/tex]