<h3 id="back-link"><a href="/#1.1">$\leftarrow$Back</a></h3>

    <h3> Statement </h3>
    <p>
        $1.1.19.$ By what angle will the direction of velocity of the ball change after two elastic impacts on the walls, the angle between which is equal to $\alpha$? How will the ball fly if the angle $\alpha = \pi/2$? The motion occurs in a plane perpendicular to the walls. In an elastic collision with a smooth stationary wall, the angle of incidence of the ball is equal to the angle of reflection.

    <h3>Solution</h3>
    <p>
        
        <p>
          When falling elastically on a horizontal plane, the angle of incidence is equal to the angle of reflection. 
        </p>
          <center>
          <figure>
            <img src="01.png" alt="1.1.19" 
              loading="lazy" width="400" />
            <figcaption>
              The point of intersection of the perpendiculars drawn on the edge of the angle
            </figcaption>
          </figure>
          </center>

        <p>
          Thus, the direction of velocity of the ball after two elastic impacts will change by the angle $\beta = 2\alpha$
        </p>
        <p>
          When $\alpha=\pi/2$, $\beta = \pi$, i.e., the ball will fly in the opposite direction..
        </p>
    </p>

    <h4>Answer</h4>
    <p>
        $β = 2α$. In the direction opposite to the initial
    </p>


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