[tex]dane:\\v_{o} = 0\\s = 120 \ m\\v = 50\frac{km}{h} =50\cdot\frac{1000 \ m}{3600 \ s} = 13,(8)\frac{m}{s}\approx13,8\frac{m}{s}\\szukane:\\a) \ t = ?\\b) \ a = ?\\\\Rozwiazaie\\\\a)\\\\s = \frac{1}{2}at^{2}\\\\ale \ a =\frac{\Delta v}{t} = \frac{v}{t}\\\\s = \frac{1}{2}\cdot\frac{v}{t}\cdot t^{2}\\\\s = \frac{1}{2}vt \ \ |\cdot2\\\\v\cdot t = 2s \ \ |:v[/tex]
[tex]t = \frac{2 \ s}{v}\\\\t = \frac{2\cdot120 \ m}{13,8\frac{m}{s}} \approx 17,4 \ s[/tex]
[tex]b)\\\\a = \frac{v}{t}\\\\a = \frac{13,8\frac{m}{s}}{17,4 \ s} \approx0,79\frac{m}{s^{2}}\approx0,8\frac{m}{s^{2}}[/tex]