Re: [Phys-L] projectiles and the spinning Earth

[Joseph Bellina <inquirybellina@comcast.net>]

A source of confusion can be the possibility of viewing the event from different frames of reference. It might be better to think of a cannon on a railroad car so the two frames the car and the ground are clear

Sent from my iPhone

> On Dec 4, 2025, at 6:23 PM, Anthony Lapinski via Phys-l <phys-l@mail.phys-l.org> wrote:
>
> This came up at lunch today, after someone watched a related video. The
> idea is to horizontally fire a gun eastward and then westward from the same
> height. Ignore air and any Coriolis effect. Most people at the table (and
> in the video) said that the one fired eastward will travel farther because
> it's in the direction of Earth's rotation. I disagreed since the gun/bullet
> have the same speed as the Earth before firing. So when you fire eastward,
> the bullet does have an extra initial velocity, but the earth is rotating *away
> from* the bullet. If you fire westward, the bullet has a smaller initial
> velocity, but the earth is rotating *toward* the bullet. The effects
> should cancel, and the bullet will travel the same distance horizontally in
> either case. I stuck to my guns (no pun intended!), but nobody at the table
> took my side! Nor was I expecting them to. Unless I am mistaken. I think
> the person said that the video showed that the actual bullet (with air
> effects) actually went farther when fired eastward.
>
> I think this is similar to planes flying cross-country eastward vs
> westward. Even though planes are not projectiles, the flight times should
> be identical. However, because of the eastward-blowing jet streams (in the
> USA), the eastward times are shorter.
>
> Any thoughts?
> _______________________________________________
> Forum for Physics Educators
> Phys-l@mail.phys-l.org
> https://www.phys-l.org/mailman/listinfo/phys-l