Ta có : \(s=15t+t^2\)

Mà : \(s=v_ot+\dfrac{1}{2}at^2\) 

\(\Leftrightarrow\left\{{}\begin{matrix}v_o=15m\backslash s\\a=0,5m\backslash s^2\end{matrix}\right.\)

\(v=v_o+at=15+0,5.3=16,5m\backslash s\)

Phỏng vấn cháu đi ông, cháu thích lắm =)))

Ta có :

\(\dfrac{W_t}{W}=\dfrac{\dfrac{1}{2}kx^2}{\dfrac{1}{2}kA^2}=\dfrac{x^2}{A^2}=\dfrac{5^2}{10^2}=\dfrac{1}{4}\)

\(\Leftrightarrow\dfrac{W_t}{W_t+W_đ}=\dfrac{1}{4}\)

\(\Leftrightarrow\dfrac{W_đ}{W_t}=3\)

Vậy...

Hề lố Hùng =)) k biết Hùng quên mình chưa :v 

a/ \(v=v_o+at\Leftrightarrow a=\dfrac{v-vo}{t}=\dfrac{10-0}{10}=1\left(m\backslash s^2\right)\)

b/ \(v=v_o+at=0+1.15=15\left(m\backslash s\right)\)

c/ \(v=v_o+at\Leftrightarrow t=\dfrac{v-v_o}{a}=\dfrac{15}{1}=15\left(s\right)\)

d/ \(s=\dfrac{1}{2}at^2=200\left(m\right)\)

\(t_1=\dfrac{s_1}{v_1}=\dfrac{\dfrac{1}{4}s}{40}=\dfrac{s}{160}\left(h\right)\)

\(t_2=\dfrac{s_2}{v_2}=\dfrac{\dfrac{3}{4}s}{60}=\dfrac{s}{80}\left(h\right)\)

\(v_{tb}=\dfrac{s}{t_1+t_2}=\dfrac{s}{\dfrac{s}{160}+\dfrac{s}{80}}=53,3\left(km\backslash h\right)\)

\(R_m=R_1+R_2=10\left(\Omega\right)\)

\(I=\dfrac{U}{R}=\dfrac{3}{10}=0,3\left(A\right)\)

Đỗ Thanh Hải nhiều kỉ niệm z mà flop quá =))) 

Bài 2 :

Ta có :

\(q_1+q_2=10^{-9}\) \(\left(1\right)\)

\(F=\dfrac{k\left|q_1.q_2\right|}{r^2}\) \(\Leftrightarrow6.10^{-9}=\dfrac{9.10^9.\left|q_1.q_2\right|}{0,03^2}\) \(\Leftrightarrow q_1.q_2=6.10^{-22}\) \(\left(2\right)\)

Từ \(\left(1\right)+\left(2\right)\Leftrightarrow...\)