Question

What is the velocity of the 6 kg ball now?

Answer 1

Given that two balls undergo elastic collision.

The mass of the first ball is m1 = 5 kg

The mass of the second ball is m2 = 6 kg.

Let us take the ball moving towards the left as positive and the ball moving towards the right as negative.

The velocity of the first ball before the collision is

`v_o1=-2\text{ m/s}`

The negative sign indicates that it moves towards the right.

The velocity of the second ball before the collision is

`v_o2=2\text{ m/s}`

The positive sign indicates that it moves towards the left.

The velocity of the first ball after the collision is

`v_f1=3\text{ m/s}`

The positive sign indicates that it moves towards the left.

We have to find the velocity of the second ball after the collision.

According to the conservation of momentum,

`m1v_o1+m2v_o2=m1v_f1+m2v_f2`

Substituting the values, the velocity of the second ball will be

`\begin{gathered} 5*(-2)+6*12=5*3+6* v_f2 \\ v_f2=(-10+12-15)/(6) \\ =-(13)/(6) \\ =-2.16\text{ m/s} \end{gathered}`

Here, the negative sign indicates that the ball is moving towards the right.

Thus, the correct option is 2.16 m/s to the right.