A molecules in a gas container hits the wall with speed 200m`//`s at an angle `30^(@)` with the normal, and reboudns with the same speed. Is momentum conserved in the collision ? Is the collision elastic or inelastic ?

Explanation

I . Velocity of molecule along the normal to the wall = `200 cos 30^(@)`
m = mass of molecule
Momentum before collision
` m xx 200 cos 30^(@) " " ….(i)`
In the above figure , here we are considering the molecule to be colliding with the horizontal wall of the conatiner . As the velocity of the molecule remains same before and after the collision , thus we can say that the initial kinetic energy of the system , i.e the molecule and the wall , remains same .
If we consider the system of the wall of teh container and the molecule , we can understand that there is no external force acting on the system . Thus , the momentum of the system will remain conserved . The momentum of the molecule colliding with the wall is equal to the momentum of the molecule of the molecular after collision and the rcoil momentum of the wall . As the recoil speed of the wall is negligible because it is very heavy as compared to the mass of the molecule , so the recoil momentum is zero .
Therefore , the collision between the molecule and the wall is elastic .