1.
[tex]dane:\\v_{o} = 0\\t = 15 \ min = 15\cdot60 \ s = 900 \ s\\v = 60\frac{km}{h} = 60\cdot\frac{1000 \ m}{3600 \ s} = \frac{50}{3} \ \frac{m}{s}\approx16,67\frac{m}{s}\\szukane:\\s = ?\\\\Rozwiazanie\\\\s = \frac{1}{2}at^{2}\\\\a = \frac{v}{t}\\\\s = \frac{1}{2}\cdot\frac{v}{t}\cdot t^{2}\\\\s = \frac{1}{2}vt\\\\s = \frac{1}{2}\cdot\frac{50}{3}\frac{m}{s}\cdot900 \ s\\\\s = 7 \ 500 \ m = 7,5 \ km[/tex]
2.
[tex]dane:\\\Delta v = 72\frac{km}{h} = 72\cdot\frac{1000 \ m}{3600 \ s} = 20\frac{m}{s}\\t = 2 \ s\\szukane:\\a = ?\\\\Rozwiazanie\\\\a = \frac{\Delta v}{t}\\\\a = \frac{20\frac{m}{s}}{2 \ s} = 10\frac{m}{s^{2}}[/tex]
3.
[tex]dane:\\v_{o} = 20\frac{m}{s}\\a = 2,5\frac{m}{s^{2}} \ - \ opoznienie\\v = 0\\szukane:\\a) \ t = ?\\b) \ s = ?\\\\Rozwiazanie\\\\a)\\a=\frac{\Delta v}{t} =\frac{v_{o}}{t} \ \ \rightarrow \ \ t = \frac{v_{o}}{a}\\\\t = \frac{20\frac{m}{s}}{2,5\frac{m}{s^{2}}} = 8 \ s\\\\b)\\s = v_{o}t -\frac{at^{2}}{2}\\\\s = 20\frac{m}{s}\cdot 8 \ s - \frac{1}{2}\cdot2,5\frac{m}{s^{2}}\cdot(8 \ s)^{2}\\\\s = 160 \ m - 80 \ m = 80 \ m[/tex]
