Given data:
* The initial velocity of the man is u_1 = 0 m/s.
* The initial velocity of the ball is u_2 = 0 m/s.
* The final velocity of the ball is v_2 = 9 m/s.
* The mass of the man is m_1 = 65 kg.
* The mass of the ball is m_2 = 3 kg.
Solution:
The initial momentum of the system is,
Substituting the known values,
The final momentum of the system is,
where v_1 is the final velocity of the man,
Substituting the known values,
According to the law of conservation of momentum,
By simplifying,
Here, the negative sign indicates the direction of motion of man is opposite to the direction of motion of ball.
Thus, the speed of the man is 0.42 meter