9.
[tex]Dane:\\v = 10\frac{m}{s}\\E_{k} = 0,5 \ kJ =0,5\cdot 1000 \ J = 500 \ J\\Szukane:\\m = ?[/tex]
Korzystamy ze wzoru na energię kinetyczną:
[tex]E_{k} = \frac{mv^{2}}{2} \ \ \ |\cdot 2\\\\mv^{2} = 2E_{k} \ \ \ /:v^{2}\\\\m = \frac{2E_{k}}{v^{2}}\\\\m = \frac{2\cdot500 \ J}{(10\frac{m}{s})^{2}} =\frac{2\cdot500 \ kg\cdot\frac{m^{2}}{s^{2}}}{100\frac{m^{2}}{s^{2}}}\\\\\boxed{m = 10 \ kg}\\\\\underline{Odp. \ B)}[/tex]
10.
[tex]Dane:\\P = 3 \ kW = 3\cdot1000 \ W = 3 \ 000 \ W\\t = 2 \ h = 2\cdot3600 \ s = 7200 \ s\\Szukane:\\W = ?[/tex]
Korzystamy ze wzoru na moc silnika:
[tex]P = \frac{W}{t} \ \ \ |\cdot t\\\\W = P\cdot t\\\\W = 3000 \ W\cdot 7200 \ s = 3000\frac{J}{s}\cdot7200 \ s\\\\\boxed{W = 21 \ 600 \ 000 \ J = 21 \ 600 \ kJ}\\\\\underline{Odp. \ B)}[/tex]
