Q. 125 Two solid spheres form aisolated system. Sphere X moves with speed \( 6 \mathrm{~cm} \mathrm{~s}^{-1} \) in a straight line directly towards?nationarp-sphere \( Y \), as shown.
The spheres have a perfectly clastic collision. After the collision, sphere \( \mathbf{X} \) moves with speed \( \mathbf{2} \mathrm{cm} \mathrm{s}^{-1} \) in the same dire tion as before the collision.
What is the spleed of sphere Y ?
A) \( 2 \mathrm{~cm} / \mathrm{s} \)
C) \( 6 \mathrm{~cm} \mathrm{~s}^{-1} \)
B) \( 4 \mathrm{~cm}^{2} \)
D) \( 8 \mathrm{~cm} \mathrm{~s}^{-1} \)