[tex]Dane:\\a = 3\frac{m}{s^{2}}\\s = 1,5 \ km = 1500 \ m\\Szukane:\\t = ?\\\\\\s = \frac{at^{2}}{2} \ \ /\cdot2\\\\at^{2} = 2s \ \ /:a\\\\t^{2} = \frac{2s}{a}\\\\t = \sqrt{\frac{2s}{a}}\\\\t = \sqrt{\frac{2\cdot1500 \ m}{3\frac{m}{s^{2}}}} = \sqrt{1000 \ s^{2}}}\\\\\boxed{t \approx 31,6 \ s}[/tex]
