4 ms·
> A parabolic trajectory would require a uniform gravitational field. A uniform gravitational field is such a good approximation for the situation described th
by fmihaila 8y ago
> A parabolic trajectory would require a uniform gravitational field.
A uniform gravitational field is such a good approximation for the situation described that I didn't think of including that proviso. Ballistic trajectory calculations close to the Earth's surface assume constant g.
- Cogito 8y agoTo clarify for anyone reading, the difference is not constant vs variable magnitude of g, it's constant vs variable direction of g. Gravity is a vector pointing at the (weighted by inverse of distance squared) centre of mass, so once you are operating on a global scale you have to account for the direction of g changing as you move around. The force always pointing towards a single point is what causes an ellipse to form. If the force always pointed down it would be a parabola, and over short distances on the surface this is a really good approximation.
- aw1621107 8y agoOnly now when re-reading your comment do I realize that you said "any throw you could possibly produce", in which case you are correct. I was thinking that you were talking more about the "fire a stupendously powerful cannon to get an orbital (or closeish) trajectory" situation, in which case the velocities would be high enough to not use a uniform gravitational field. My apologies for the misunderstanding.