3.
[tex]dane:\\m = 120 \ kg\\h = 180 \ cm = 1,8 \ m\\g = 10\frac{m}{s^{2}} = 10\frac{N}{kg}\\szukane:\\E_{p} = ?\\\\\\E_{p} = mgh\\\\E_{p} = 120 \ kg\times10\frac{N}{kg}\times1,8 \ m\\\\\underline{E_{p} = 2 \ 160 \ J = 2,16 \ kJ}[/tex]
4.
[tex]dane:\\P = 1 \ 500 \ W\\t = 12 \ min = 12\times60 \ s = 720 \ s\\szukane:\\W = ?\\\\\\P = \frac{W}{t} \ \ /\cdot t\\\\W = P\times t \\\\W = 1500 \ W\times720 \ s\\\\\underline{W = 1 \ 080 \ 000 \ J =1 \ 080 \ kJ = 1,08 \ MJ}\\\\1 \ kJ = 1000 \ J\\1 \ MJ = 1 \ 000 \ 000 \ J[/tex]
5.
[tex]dane:\\v = 20\frac{m}{s}\\g = 10\frac{m}{s^{2}}\\szukane:\\h = ?\\\\\\t = \frac{v}{g} = \frac{20\frac{m}{s}}{10\frac{m}{s^{2}}} = 2 \ s\\\\h = \frac{1}{2}gt^{2}\\\\h = \frac{1}{2}\times10\frac{m}{s^{2}}\times(2 \ s)^{2}\\\\\underline{h = 20 \ m}[/tex]
