An 80-kg quarterback jumps straight up in the air right before throwing a 0.43-kg football horizontally at 15 m/s. how fast will he be moving backward just after releasing the ball?

Applying conservation of momentum

Quarterback mass = 80 kg

ball mass = 0.43 kg

Initially both together but horizontal velocity of both 0

initial momentum = 0

Final momentum = 15*0.43 - 80v

initial = final (law of conservation of momentum)

6.45 = 80v

v = 0.08 m/s