BITSAT 2016 Paper

Given m1=m2
We will apply the principle of conservation of momentum in the mutually perpendicular dirn
Along x-axis m1u1=m1v1‌cos‌θ+m2v2‌cos‌ϕ
or u1=v1‌cos‌θ+v2‌cos‌ϕ....(1)
Along y-axis 0=m1v1‌sin‌θ−m2v2‌sin‌ϕ
or 0=v1‌sin‌θ−v2‌cos‌ϕ......(2)
Again for elastic collision, kinetic energy is conserved
⇒‌‌

1

2

mu12=‌‌

1

2

mv12+‌‌

1

2

mv22
or u12=v12+v22 ....(iii)
Squaring and adding (i) & (ii), we get
Using (iii) & (iv), we get
Note : This is a standard case of oblique collision.