1.
[tex]Dane:\\s = 40 \m\\F = 120 \ N\\Szukane:\\W = ?\\\\\\W = F\cdot s\\\\W = 120 \ N\cdot 40 \ m\\\\\boxed{W = 4 \ 800 \ J = 4,8 \ kJ}\\\\(1 \ kJ = 1000 \ J)[/tex]
2.
[tex]Dane:\\m = 500\cdot20 \ kg = 1000 \ kg\\W = 10 \ 000 \ J\\g = 10\frac{m}{s^{2}} = 10\frac{N}{kg}\\Szukane:\\h = ?\\\\\\W = E_{p} = mgh\\\\W = mgh \ \ \ |:mg\\\\h = \frac{W}{mg}\\\\h = \frac{10000 \ J}{1000 \ kg\cdot10\frac{N}{kg}} = \frac{1000 \ N\cdot m}{1000 \ N}\\\\\boxed{h = 1 \ m}[/tex]
3.
[tex]Dane:\\t = 5 \ min = 5\cdot60 \ s = 300 \ s\\W = 1,2 \ MJ = 1,2\cdot1000000 \ J = 1 \ 200 \ 000 \ J\\Szukane:\\P = ?\\\\\\P = \frac{W}{t}\\\\P = \fracP1200000 \ J}{300 \ s}\\\\\boxed{P = 4 \ 000 \ W = 4 \ kW}[/tex]
4.
[tex]Dane:\\F = 50 \ kN = 50 \ 000 \ N\\v = 1\frac{m}{s}\\Szukane:\\P = ?\\\\\\P = \frac{W}{t}=\frac{F\cdot s}{t} \\\\ale: \ \ \frac{s}{t} = v\\\\P = F\cdot v\\\\P = 50000 \ N\cdot1\frac{m}{s} = 50000\frac{kg\cdot m}{s^{2}}\cdot1\frac{m}{s}=50 \ 000\frac{kg\cdot m^{2}}{s^{3}}}\\\\\boxed{P = 50 \ 000 \ W = 50 \ kW}[/tex]
