[tex]dane:\\v = 40\frac{km}{h} = 40\cdot\frac{1000 \ m}{3600 \ s} = \frac{100}{9} \ \frac{m}{s}\\s = 400 \ m\\szukane:\\t = ?\\\\v = \frac{s}{t} \ \ \rightarrow \ \ t = \frac{s}{v}\\\\t = \frac{400 \ m}{\frac{100}{9}\frac{m}{s}} = \frac{400\cdot9}{100} \ s\\\\\boxed{t = 36 \ s}[/tex]
Odp. Szukany czas to t = 36 s.
