Question

Решить задачу по физике (вторую)

Answer 1

S:3S:4S:2S  
2t:4t:3t:t
v4 = 80 
v(ср)= (S1+S2+S3+S4)/t1+t2+t3+t4
v4 = 80 = S4 /t4 = 2S/t  ; t=S/40
2) S1= S; S2 =3S ;S3=4S; S4=2S ;
    t1= 2S/40;t2 = 3S/40; t3=4S/40 ;t4= 2S/40
v(ср)=(S+3S+4S+2S)/(2S/40+3S/40+4S/40+S/40)= 10S*40/10S= 40 км/ч

отв: v(ср)= 40 км/ч