[tex]dane:\\m = 1000 \ kg\\v_1 = 54\frac{km}{h} = 54\cdot\frac{1000 \ m}{3600 \ s} = 15\frac{m}{s}\\v_2 = 72\frac{km}{h} = 72\cdot\frac{1000 \ m}{3600 \ s} = 20\frac{m}{s}\\szukane:\\\Delta E_{k} = ?\\\\Rozwiazanie\\\\E_{k} = \frac{mv^{2}}{2}\\\\\Delta E_{k} = E_{k_2} - E_{k_1}\\\\\Delta E_{k} = \frac{mv_2^{2}}{2}-\frac{mv_1^{2}}{2} = \frac{m}{2}(v_2^{2}-v_1^{2})\\\\\Delta E_{k} = \frac{1000 \ kg}{2}\cdot[(20\frac{m}{s})^{2}-(15\frac{m}{s})^{2}][/tex]
[tex]\Delta E_{k} = 500 \ kg \cdot(400\frac{m^{2}}{s^{2}}-225\frac{m^{2}}{s^{2}})\\\\\Delta E_{k} = 500 \ kg\cdot175\frac{m^{2}}{s^{2}} = 87 \ 500 \ J = 87,5 \ kJ\\\\(1 \ kJ = 1000 \ J)[/tex]
Odp. Energia samochodu wzrosła o 87 500 J (87,5 kJ).
