V=300+400=700 м/c
...........................................................................
I1=I2
I1=U1/R1
I2=U2/R2
U1/R1=U2/R2=>U2=U1*R2/R1
U2=12B
U=U1+U2
U=15B
I=I1
I=U1/R1
I=0,3 A
R=R1+R2
R=50 Oм
M = 3 т = 3000 кг
V0 = 72 км/ч = 20 м/с
S = 200 м
F ср. - ?
t = S/V0 = 200/20 = 10 с
a = V-V0/t = 0-20/10 = -2 м/с^2
F = ma = 3000*(-2) = -6000 Н = -6 кН
.........................
X=s-s1
s1=v0-at^2/2
s1=10-3*2^2/2=4 м
х=100-4=96 м