Let’s do a quick thought experiment. Let’s say you’re tossing a cannonball in your hand, and the mage shrinks it just as it leaves your hand (maximum momentum). If momentum is conserved, the cannonball would have to dramatically increase speed to conserve momentum.
shrunken size would be about a marble, with a mass of ~2.7g
Initial momentum of the cannonball would be 83.6 kg·m/s. If momentum is conserved, the marble would travel 30963 m/s, or Mach 90. That’s unreasonable.
So for this to make any sense, conservation of momentum shouldn’t be preserved. In other words, mass would be added with the current velocity, so it would increase momentum as it unshrinks.
Why assume a conservation of momentum?
Let’s do a quick thought experiment. Let’s say you’re tossing a cannonball in your hand, and the mage shrinks it just as it leaves your hand (maximum momentum). If momentum is conserved, the cannonball would have to dramatically increase speed to conserve momentum.
Example data/assumptions:
Initial momentum of the cannonball would be 83.6 kg·m/s. If momentum is conserved, the marble would travel 30963 m/s, or Mach 90. That’s unreasonable.
So for this to make any sense, conservation of momentum shouldn’t be preserved. In other words, mass would be added with the current velocity, so it would increase momentum as it unshrinks.