I read recently that if you hold a bullet in one hand and a pistol in the other, both hands at the same height, and subsequently fired the pistol at the same time as dropping the bullet, both bullets would hit the ground at the same time (assuming the fired bullet encounters no obstacles).
Is this true, and if so can you explain the reasoning behind it with as few equations as possible? I assume it is essentially that gravity is unaffected by momentum, but it just sounds counter-intuitive.
Answer
This is indeed true. The easiest way to think about it is in planes. You have horizontal and vertical planes for velocity and acceleration. For both bullets, there is initially no vertical velocity and the only net force acting upon them is gravity. You would then expect them to act similarly in the vertical plane, which is why they both hit the ground at the same time. There is nothing in the forward motion of the shot bullet that counteracts the pull downward from gravity (such as lift). I hope that explanation isn't too vague and helps you understand better what is going on.
EDIT: I should specify that this only holds true for ideal situations (being in a vacuum, no air resistance, etc.)
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