Question

un mobil are viteza 5km/h pe 1/4 din drumul sau ,iar pe restul drumului are viteza 10m/s. Sa se calculeze viteza medie, SI DISTANTA PARCURSA in durata de timp 20s. VAAAA Rooooooog e urgent dau coroana si inima plssss

Answer 1

$v_2=10 m/s=36 km/h\\d_1=\frac{d}{4}\\ d_1+d_2=d=>d_2=d-d_1=d-\frac{d}{4}=\frac{3d}{4}\\t_1+t_2=t\\d_1=v_1t_1=>t_1=\frac{d_1}{v_1}=\frac{d}{4v_1}\\d_2=v_2t_2=>t_2=\frac{d_2}{v_2}=\frac{3d}{4v_2}\\d=v_m*t=>v_m=\frac{d}{t}=\frac{d}{\frac{d}{4v_1}+\frac{3d}{4v_2}}=\frac{1}{\frac{v_2+3v_1}{4v_1v_2} }=\frac{4v_2v_1}{3v_1+v_2}=\frac{4*5*36}{3*5+36}=\frac{720}{51}=14,11km/h=50,82 m/s=>v_m=50,82 m/s$

$t'=20 s\\d'=v_m*t'=50,82*20=1016,4 m=>d'=1016,4 m$