Collision of ball with a fixed inclined plane

[Dr.azwar]

if a ball of mass m were to strike an fixed incined plane of 45degress with velocity of 3m/s, and was rebounded horizontally, what would be the velocity of the rebounded ball.(elastic collision). this the method i have tried.
momentum of the system along the x-axis is conserved.therefore,
m(0)+M(0)=M(0)+m(x) (M is mass of incline plane)
therefore velcoity of ball is 0
where am i making the mistake

 

[Simon Bridge]

Examine your assumption. Why would the horizontal momentum be conserved?

Hint: "elastic collision"?

 

[Dr.azwar]

could you please show me the solution

 

[Simon Bridge]

could you please show me the solution

I could but I won't, it's not allowed.
Its your homework, you have to figure it out.
I can point in the right direction and ask guiding questions, that's all.

What does "elastic collision" mean? You will have some course notes with those words in them. Go look.
Alternatively you could try googling for the meaning.
http://hyperphysics.phy-astr.gsu.edu/hbase/elacol.html