7.
[tex]dane:\\s_1 = 20 \ km\\t_1 = 5 \ h\\s_2 = 4 \ km\\t_2 = 3 \ h\\szukane:\\v_{sr} = ?\\\\Rozwiazanie\\\\v_{sr} = \frac{s}{t}\\\\s = s_1 + s_2 = 20 \ km + 4 \ km = 24 \ km\\\\t = t_1+ t_2 = 5 \ h + 3 \ h = 8 \ h\\\\v_{sr} = \frac{24 \ km}{8 \ h}\\\\\underline{v_{sr} = 3\frac{km}{h}}[/tex]
9.
[tex]dane:\\v_{o} = 0\\t = 3 \ s\\v = 12\frac{m}{s}\\szukane:\\a = ?\\\\Rozwiazanie\\\\a = \frac{\Delta v}{t} = \frac{v-v_{o}}{t} = \frac{v}{t}\\\\a = \frac{12\frac{m}{s}}{3 \ s}\\\\\underline{a = 4\frac{m}{s^{2}}}[/tex]
10.
[tex]dane:\\v_{o} = 0\\a = 6\frac{m}{s^{2}}\\t = 3 \ s\\szukane:\\a) \ v = ?\\b) \ s = ?\\\\Rozwiazanie\\\\a)\\v = a\cdot t\\\\v = 6\frac{m}{s^{2}}\cdot3 \ s\\\\\underline{v = 18\frac{m}{s}}\\\\b)\\s = \frac{1}{2}at^{2}}\\\\s = \frac{1}{2}\cdot6\frac{m}{s^{2}}\cdot(3 \ s)^{2}\\\\\underline{s = 27 \ m}[/tex]
