Strange wall-ball problem

Okay I get it - the title is not that imaginitive.
Hi there! The organic post that was to be never came up because I left my copy back in school but its some pretty interesting isomerism nuts that I was shown by my teacher. For now its some physics- collision style!
In fiitjee and other study mats there is always this obscure thing that concerns a ball with a wall. (Wall=infinite mass, ball=m)When the ball collides with the wall having an initial velocity u it returns back with the same velocity provided that the collision is elastic. Now fix the ball, let the wall strike the ball with a velocity u.Whatt happens now?

Contrary to all common sense the ball lurches forward with a velocity 2u.why??
A friend of mine kaustav sengupta (never mind the too erudite tone of the sentence) made sense when he said that consider the first case as in figure1, the frame instead of being stationary with respect to the ground is having a velocity u to its right. then?/Â…..we get the second case, fig2, minus the comment about not making sense.
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the return of sith :-)

hi there! i came back from skool yesterday and went through the whole blog. the idea was great i think.to start a blog that lays importance to the subtle nuances of physics and maths(not much of a chemistry there).and i m rlly happy that the posts have not dried up.as per catching up - it was good to hear that ftse was actually a mess. u know wat? a friend of a friend of mine,mutual friend that is, reads in fiitjee delhi classroom courses and he told us that they were taught in advance in the discussion classes abt 80% of the sums - a leak if there ever was one.assuming of course that he wasnt, u know, throwing off.anyway i was down in confidence for weeks.sort of brings things into perspective, doesnt it?
anyway i will be posting one on organic pretty soon - its been neglected for long.
pss:i will be staying here till 27th.then i wont come back to home till march.