If after the collision, the direction of the ball's velocity is reversed, and the bar has both rotational and translational motion, if the collision is elastic, both momentum and kinetic energy is conserved.
According to law of conservation of momentum,
m1 u1 + m2 u2 = m1 v1 + m2 v2
m1 u1 = Initial momentum of object A
m2 u2 = Initial momentum of object B
m1 v1 = Final momentum of object A
m2 v2 = Final momentum of object B
According to law of conservation of energy,
1 / 2 m1 u1² + 1 / 2 m2 u2² = 1 / 2 m1 v1² + 1 / 2 m2 v2²
1 / 2 m1 u1² = Initial kinetic energy of object A
1 / 2 m2 u2² = Initial kinetic energy of object B
1 / 2 m1 v1² = Final kinetic energy of object A
1 / 2 m2 v2² = Final kinetic energy of object B
Therefore, if the collision is elastic, both momentum and kinetic energy is conserved.
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