Bronco dives from a hovering helicopter and finds his momentum increasing Does this violate the conservation of momentum?

Answer 1

If you're only looking at Bronco, then it certainly seems to, doesn't it. That's

because you're only looking at a part of the system, not the whole system.

The whole system is the combination of Bronco and the Earth. When Bronco

releases his grip on the helicopter's skid, and begins to fall, you have to look

at both sides of the system.

There is a pair of mutual, equal gravitational forces, attracting Bronco and the

Earth toward each other, so both objects accelerate toward each other. The

accelerations are in inverse proportion to the masses, so Bronco picks up somewhat

more speed toward the Earth than the Earth picks up toward Bronco. But both

of them are moving toward their common center of mass, and they're obviously

moving in opposite directions.

Bronco's speed multiplied by his mass is his momentum, directed downward. The

Earth's tiny speed, multiplied by its large mass, is its momentum, directed upward.

They're equal, and they're opposite, and they add up to zero, just like the momentum

of the system before Bronco jumped.

QED