Zad 21, 23 ze zdjecia w zalczniku

21. D: V1=54km/h=15m/s S: t=? h=? V2=? t=tw+ts (czas wznoszenia, czas spadania) tw = ts t=2tw V1=tw*a tw=V/a tw=15/10= 1,5 [s] t = 3s [latex]h= frac{at^{2} }{2} [/latex] [latex]h _{1} = frac{10 frac{m}{ s^{2} } *2,25 s^{2} }{2} = 11,25m[/latex] h_{2}=2*h_{1}=11,25 m * 2 = 22,5 m h_{2}=[latex] frac{at^{2} }{2} [/latex] t^{2}=[latex] frac{2h}{a} [/latex] t=[latex] sqrt{ frac{2h}{a} } [/latex] t=[latex] sqrt{ frac{45}{10} }= sqrt{4,5}s [/latex] V2=at_{2} V2=[latex]10sqrt{4,5} [/latex]≈21,2m/s≈76,7km/h 23. Dane: t=15s S=75m Szukane: a=? [latex] V_{0} [/latex]=? S=[latex] frac{at^{2} }{2} [/latex] a=[latex] frac{2S}{ t^{2} } [/latex] a=[latex] frac{150m}{225s^{2} } = frac{2}{3} frac{m}{ s^{2} } [/latex] [latex]V_{0} =a*t= frac{2}{3} frac{m}{ s^{2} } *15s=10 frac{m}{s} [/latex]