= Solution
Adding tangential <velocity> along the existing motion increases both <orbital energy> and <angular momentum>:
$$
\Delta E=m v_c\delta+\frac12m\delta^2>0,\qquad \Delta L=m r_0\delta>0.
$$
For a sufficiently small kick the <Kepler orbit> remains an <ellipse>. At the kick point its radial <velocity> vanishes and its tangential <speed> exceeds the <circular orbital speed>, so that point becomes the <pericentre>. \b[The ellipse extends farther outward than the original circle.]
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