A projectile is launched with speed u at angle α from a point distance d from a smooth vertical wall. After rebounding it returns to the launch point. The maximum d for which this is possible is:
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A projectile is launched with speed u at angle α from a point distance d from a smooth vertical wall. After rebounding it returns to the launch point. The maximum d for which this is possible is:

G1 Physics · Accepted Answer

Use conservation of linear momentum together with e = (relative speed of separation)/(relative speed of approach). Solving the two collision equations gives A: eu²/[g(1+e)].