Answer:
0.081 m /s
Explanation:
According to the conservation of momentum, the momentum of a system is conserved when no external force is applied on a body.
momentum of the system before throwing = momentum of the system after throwing
Let v be the velocity of quarterback after throwing the football.
80 x 0 + 0.43 x 0 = 80 x v + 0.43 x 15
0 = 80 v + 6.45
v = - 0.081 m /s
The negative sign shows that he is moving in backward direction.