Ta có: \(\widehat{i}=\widehat{i'}=30^0\)

Bài 1:

a) \(R_{tđ}=\dfrac{R_1.R_2}{R_1+R_2}=\dfrac{6.12}{6+12}=4\left(\Omega\right)\)

b) Do mắc song song nên

\(U=U_1=U_2=4,8V\)

Cường độ dòng điện I1:

\(I_1=\dfrac{U_1}{R_1}=\dfrac{4,8}{6}=0,8\left(A\right)\)

Cường độ dòng điện I2:

\(I_2=\dfrac{U_2}{R_2}=\dfrac{4,8}{12}=0,4\left(A\right)\)

Bài 2:

Do R1//R2//R3

\(\Rightarrow\dfrac{1}{R_{tđ}}=\dfrac{1}{R_1}+\dfrac{1}{R_2}+\dfrac{1}{R_3}=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{16}=\dfrac{5}{16}\)

\(\Rightarrow R_{tđ}=3,2\left(\Omega\right)\)

Nhường bé tí coi :(

\(1,\Rightarrow\left\{{}\begin{matrix}a,\Rightarrow a=\dfrac{v-vo}{t}=\dfrac{15}{60}=0,25m/s^2\\b,\Rightarrow S=vot+\dfrac{1}{2}at^2=\dfrac{1}{2}at^2=\dfrac{1}{2}.0,25.60^2=450m\end{matrix}\right.\)

\(2.\Rightarrow\left\{{}\begin{matrix}a,\Rightarrow a=\dfrac{v^2-vo^2}{2S}=\dfrac{10^2-5^2}{2.50}=0,75m/s^2\\b,\Rightarrow t=\dfrac{v-vo}{a}=\dfrac{10-5}{0,75}=6,67s\\\end{matrix}\right.\)

\(3.\Rightarrow\left\{{}\begin{matrix}a,\Rightarrow a=\dfrac{15-10}{10}=0,5m/s^2\\b,\Rightarrow S=vot+\dfrac{1}{2}at^2=10.t+\dfrac{1}{2}at^2=10.30+\dfrac{1}{2}.0,5.30^2=525m\\\end{matrix}\right.\)

\(4.\Rightarrow\left\{{}\begin{matrix}\Rightarrow\dfrac{v^2-vo^2}{2S}=a\Rightarrow S=\dfrac{v^2-vo^2}{2a}=\dfrac{10^2}{2.0,1}=500m\\\Rightarrow500=vot+\dfrac{1}{2}at^2=\dfrac{1}{2}at^2\Rightarrow t=100s\\\end{matrix}\right.\)

\(5.av< 0\Rightarrow\left\{{}\begin{matrix}a=\dfrac{v^2-vo^2}{2S}=\dfrac{0^2-10^2}{2.20}=-2,5m/s^2\\20=vot+\dfrac{1}{2}at^2=10t+\dfrac{1}{2}\left(-2,5\right)t^2\Rightarrow t=4s\\\end{matrix}\right.\)

\(6.\Rightarrow\left\{{}\begin{matrix}a,\Rightarrow a=\dfrac{10-20}{10}=-1m/s^2\\b,\Rightarrow S=\dfrac{v^2-vo^2}{2a}=\dfrac{10^2-20^2}{-2}=150m\\c,\Rightarrow v=vo+at=20+\left(-1\right).15=5m/s\\\end{matrix}\right.\)

\(7.\) chọn\(O\equiv A\), chiều (+) l à chiều chuyển động, mốc tgian lúc xe chuyển động\(\Rightarrow v>0\)

\(\Rightarrow\)\(\Rightarrow av< 0\Rightarrow S=\dfrac{v^2-vo^2}{-2a}=\dfrac{5^2-10^2}{-2.2}=18,75m\)

\(8.tương\) \(tự\) \(mấy\) \(bài\) \(trên\)

Có viết thêm chữ N sau số 10 không bạn