Question

va rog decat 5 si 6 acelea cu T

Answer 1

$t_1=t_{2$
$v_1=15 m/s$
$v_2= 90 km/h= 90000m/3600s=25 m/s$
$v_m= \frac{d_1+d_2}{t_1+t_2}$
$v= \frac{d}{t} ==\ \textgreater \ d=v*t$
$d_1=v_1*t_1=15t_1$
$d_2=v_2*t_2= 25t_1$
$v_m= \frac{15t_1+25t_1}{2t_1} = \frac{40t_1}{2t_1} =20m/s$

 $d_1= \frac{d}{2}$ $d_2= \frac{d}{2}$ $d_1+d_2=d$
 $v_1=54 km/h =54000m/3600s=15 m/s$ $v_2=25 m/s$ 
$v_m= \frac{d_1+d_2}{t_1+t_2}$ $v= \frac{d}{t} ==> t= \frac{d}{v}$ 
$t_1= \frac{ \frac{d}{2} }{15} = \frac{d}{30}$ 
$t_2= \frac{ \frac{d}{2} }{25} = \frac{d}{50}$ 
$v_m=  \frac{d}{\frac{d}{30}+\frac{d}{50}}$ 
$v_m=  \frac{d}{\frac{5d+3d}{150}}$ 
$v_m=  \frac{d}{\frac{8d}{150}$ 
$v_m=  \frac{150}{8}$
 $v_m=   18.75$