Ek [J] m [kg] v [m/s
========================
40 20 2
----------------------------------------
400 50 4
----------------------------------------
100 8 5
----------------------------------------
[tex]E_{k} = \frac{mv^{2}}{2} \ \ /\cdot\frac{2}{m}\\\\v^{2} = \frac{2E_{k}}{m}\\\\1) \ v = \sqrt{\frac{2E_{k}}{m}} = \sqrt{\frac{2\cdot40}{20}} \ [\frac{m}{s}] =\sqrt{4} \ [\frac{m}{s}] = 2[\frac{m}{s}]\\\\\\2) \ E_{k} = \frac{mv^{2}}{2}=\frac{50\cdot4^{2}}{2} \ [J] = 400 \ [J]\\\\\\E_{k} = \frac{mv^{2}}{2} \ \ /\cdot\frac{2}{v^{2}}\\\\3) \ m = \frac{2E_{k}}{v^{2}} = \frac{2\cdot100}{5^{2}} \ [kg] = \frac{200}{25} \ [kg] = 8 \ [kg][/tex]
