Question

You are playing pool and shoot ball A with initial velocity Vai. After it collides elastically with ball B, the two balls have velocities Vaf and Bbf. What is Vbf if Vai is 3(m/s)j and the angle between Vaf and Vbf is 60 degrees?

Answer 1

As you have not mentioned the mass of the two balls. So, i am considering mass of ball A is m_A and mass of ball B is m_B .

Given,

NOTE : For simplicity , i am considering the direction of v_ai in positive x - direction.

We have,

  

So,

or we can write ,

  

or, ...........................................(1)

And

  

or,  

or, ...............................................(2)

Now if m_A = m_B then , from equation (1)

  

putting these in equation (2), we get

  

or,

For any doubt please comment.