Answer:

Step-by-step explanation:
given,
scattering angle of alpha particle = 25.0° above its initial direction of motion
oxygen nucleus recoils at = 50.0° below this initial direction.
final speed of the oxygen = 2.08×10⁵ m/s
mass of alpha particle = 4.0 u
mass o oxygen nucleus = 16 u
momentum conservation along x- axis


....(1)
Along y-direction




putting value in equation (1)

