Solution
= Solution
For a small opposing tangential kick,
$$
\Delta E=-m v_c\delta+\frac12m\delta^2<0,\qquad \Delta L=-m r_0\delta<0.
$$
The new tangential <speed> is less than the <circular orbital speed>, so the kick point is the <apocentre> of an <ellipse>. \b[The orbit falls inward from the original circle.] The signs assume $0<\delta\ll v_c$; a large velocity reversal is outside the stated small-impulse regime.