1.
[tex]dane:\\m = 7 \ kg\\v = 20\frac{m}{s}\\szukane:\\E_{k}=?\\\\Rozwiazanie\\\\E_{k} = \frac{1}{2}mv^{2}\\\\E_{k} = \frac{1}{2}\cdot7 \ kg\cdot(20\frac{m}{s})^{2}}\\\\E_{k} = 1 \ 400 \ J = 1,4 \ kJ[/tex]
2.
[tex]dane:\\m = 3\cdot200 \ g = 600 \ g = 0,6 \ kg\\h = 8 \ m\\g = 10\frac{m}{s^{2}}\\szukane:\\E_{p} = ?\\\\Rozwiazanie\\\\E_{p} = mgh\\\\E_{p} =0,6 \ kg\cdot10\frac{m}{s^{2}}\cdot8 \ m\\\\E_{p} = 48 \ J[/tex]
3.
[tex]dane:\\v = 108\frac{km}{h} = 108\cdot\frac{1000 \ m}{3600 \ s} = 30\frac{m}{s}\\E_{k} = 900 \ J = 900 \ \frac{kg\cdotm^{2}}{s^{2}}\\szukane:\\m = ?\\\\Rozwiazanie\\\\E_{k} = \frac{mv^{2}}{2} \ \ |\cdot\frac{2}{v^{2}}\\\\m = \frac{2E_{k}}{v^{2}}}\\\\m = \frac{2\cdot900\frac{kg\cdot m^{2}}{s^{2}}}{(30\frac{m}{s})^{2}}\\\\m = 2 \ kg[/tex]
