Đáp án:
\({x_3} = 4cm\)
Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
{\left( {\dfrac{{{x_1}}}{A}} \right)^2} + {\left( {\dfrac{{{v_1}}}{{{v_{\max }}}}} \right)^2} = 1\\
\Rightarrow {\left( {\dfrac{3}{A}} \right)^2} + {\left( {\dfrac{{40}}{{50}}} \right)^2} = 1\\
\Rightarrow A = 5cm
\end{array}\)
Mặt khác:
\(\begin{array}{l}
{\left( {\dfrac{{{x_3}}}{A}} \right)^2} + {\left( {\dfrac{{{v_3}}}{{{v_{\max }}}}} \right)^2} = 1\\
\Rightarrow {\left( {\dfrac{{{x_3}}}{5}} \right)^2} + {\left( {\dfrac{{30}}{{50}}} \right)^2} = 1\\
\Rightarrow {x_3} = 4cm
\end{array}\)