7.
[tex]dane:\\m = 350 \ kg\\h_1 = 2,5 \ m\\h_2 = 5 \ m\\\Delta h = h_2-h_1 = 5 \ m - 2,5 \ m = 2,5 \ m\\g = 10\frac{N}{kg}\\szukane:\\\Delta E_{p} = ?\\\\Rozwiazanie\\\\\Delta E_{p} = m\cdot g\cdot \Delta h\\\\E_{p} = 350 \ kg\cdot10\frac{N}{kg}\cdot2,5 \ m = 8 \ 750 \ J\\\\Odp. \ A[/tex]
8.
[tex]dane:\\m = 3 \ kg\\v = 108\frac{km}{h} = 108\cdot\frac{1000 \ m}{3600 \ s} = 30\frac{m}{s}\\h = 1,75 \ km = 1 \ 750 \ m\\g = 10\frac{m}{s^{2}}\\szukane:\\E_{c} = ?\\\\Rozwiazanie\\\\E_{c} = E_{p} + E_{k}\\\\E_{p} = mgh = 3 \ kg\cdot10\frac{m}{s^{2}}\cdot1750 \ m = 52 \ 500 \ J\\\\E_{k} = \frac{1}{2}mv^{2} = \frac{1}{2}\cdot3 \ kg\cdot(30\frac{m}{s})^{2} = 1 \ 350 \ J\\\\E_{c} = 5 2500 \ J + 1350 \ J = 53 \ 850 \ J = 53,85 \ kJ\\\\Odp. \ D.[/tex]
9.
[tex]dane:\\m = 15 \ dag = 0,15 \ kg\\E_{k} = 4,5 \ J\\szukane:\\H = ?\\\\Rozwiazanie\\\\Z \ zasady \ zachowania \ energii\\\\E_{k} = E_{p} = mgH\\\\E_{k} = mgH \ \ /:mg\\\\H = \frac{E_{k}}{m\cdot g}\\\\H = \frac{4,5 \ J}{0,15\cdot10\frac{m}{s^{2}}} = \frac{4,5 \ kg\cdot\frac{m^{2}}{s^{2}}}{1,5\frac{m}{s^{2}}}=3 \ m\\\\Odp. \ B.[/tex]
