Answer:
6 m/s
Explanation:
The law of conservation of momentum states that the momentum before collision will be equal to the momentum after collision. Momentum is the product of mass and velocity.
Given that the two bodies were moving in opposite direction and the velocity after collision was 0, let the velocity of the tackle before collision be h
Then
(86 × 9) - 129h = (129 + 86) × 0
129h = 86 × 9
h = 86 × 9/129
h = 6 m/s