\(30ph=\dfrac{1}{2}h\)

\(\left\{{}\begin{matrix}S=v_1.t_1=60.\left(t_2-\dfrac{1}{2}\right)\\S=v_2.t_2=40.t_2\end{matrix}\right.\)

\(\Rightarrow60\left(t_2-\dfrac{1}{2}\right)=40t_2\Rightarrow t_2=\dfrac{3}{2}\left(h\right)\)

\(\Rightarrow S_{AB}=t_2.v_2=\dfrac{3}{2}.40=60\left(km\right)\)

Ta có: \(p=d.h\)

Mà \(d_A=d_B,\) từ hình ta thấy \(h_A< h_B\)

\(\Rightarrow p_A< d_B\)

\(R_{23}=R_2+R_3=2+4=6\left(\Omega\right)\)

\(R_{tđ}=\dfrac{R_1.R_{23}}{R_1+R_{23}}=\dfrac{6.6}{6+6}=3\left(\Omega\right)\)

\(U=U_1=U_{23}=I.R_{tđ}=2.3=6\left(V\right)\)

\(\left\{{}\begin{matrix}I_1=\dfrac{U_1}{R_1}=\dfrac{6}{6}=1\left(A\right)\\I_2=I_3=\dfrac{U_{23}}{R_{23}}=\dfrac{6}{6}=1\left(A\right)\end{matrix}\right.\)

\(\left\{{}\begin{matrix}P_1=U_1.I_1=6.1=6\left(W\right)\\P_2=U_2.I_2=2.1=2\left(W\right)\\P_3=U_3.I_3=4.1=4\left(W\right)\end{matrix}\right.\)

Bài 1:

\(R_{tđ}=R_1+R_2+R_3=7+3+2=12\left(\Omega\right)\)

\(I=I_1=I_2=\dfrac{U}{R_{tđ}}=\dfrac{24}{12}=2\left(A\right)\)

\(\left\{{}\begin{matrix}U_1=I_1.R_1=2.7=14\left(V\right)\\U_2=I_2.R_2=2.3=6\left(V\right)\\U_3=I_3.R_3=2.2=4\left(V\right)\end{matrix}\right.\)

Bài 2:

\(R_{tđ}=\dfrac{R_1.R_2}{R_1+R_2}=\dfrac{3.6}{3+6}=2\left(\Omega\right)\)

\(U=U_1=U_2=2,4V\)

\(\left\{{}\begin{matrix}I=\dfrac{U}{R_{tđ}}=\dfrac{2,4}{2}=1,2\left(A\right)\\I_1=\dfrac{U_1}{R_1}=\dfrac{2,4}{3}=0,8\left(A\right)\\I_2=\dfrac{U_2}{R_2}=\dfrac{2,4}{6}=0,4\left(A\right)\end{matrix}\right.\)

\(20cm^2=0,002m^2\)

\(p=\dfrac{F}{S}=\dfrac{P}{S}=\dfrac{10m}{S}=\dfrac{10.40}{0,002}=200000\left(Pa\right)\)

\(v_1=\dfrac{S_1}{t_1}=\dfrac{2,5.1000}{2000}=1,25\left(\dfrac{m}{s}\right)\)

\(v_2=\dfrac{S_2}{t_2}=\dfrac{1,5.1000}{1000}=1,5\left(\dfrac{m}{s}\right)\)

\(v_{tb}=\dfrac{S_1+S_2}{t_1+t_2}=\dfrac{2,5.1000+1,5.1000}{2000+1000}=\dfrac{4}{3}\left(\dfrac{m}{s}\right)\)

\(800\left(\dfrac{kg}{m^3}\right)=8000\left(\dfrac{N}{m^3}\right),20cm=0,2m\)

\(p=d.h=8000.\left(1,8-0,2\right)=12800\left(Pa\right)\left(C\right)\)