1.
[tex]Dane:\\m = 5 \ kg\\F = 20 \ N\\v_1 = 15\frac{m}{s}\\v_2 = 35\frac{m}{s}\\\Delta v = v_2-v_1 = 35\frac{m}{s}-15\frac{m}{s} = 20\frac{m}{s}\\Szukane:\\t = ?\\\\Rozwiazanie\\\\a = \frac{F}{m}\\oraz\\a = \frac{\Delta v}{t}\\\\\frac{F}{m} = \frac{\Delta v}{t}\\\\t = \frac{\Delta v\cdot m}{F}\\\\t = \frac{20\frac{m}{s}\cdot 5 \ kg}{20 \ N} = \frac{100 \ kg\cdot\frac{m}{s}}{20 \ kg\cdot\frac{m}{s^{2}}}\\\\\boxed{t = 5 \ s}[/tex]
2.
[tex]Dane:\\v_{o} = 0\\v = 30\frac{m}{s}\\g = 10\frac{m}{s^{2}}\\Szukane:\\t = ?\\\\Rozwiazanie\\\\v = g\cdot t \ \ |:g\\\\t = \frac{v}{g}\\\\t = \frac{30\frac{m}{s}}{10\frac{m}{s^{2}}}\\\\\boxed{t = 3 \ s}[/tex]
