# Fireing projectile from north pole to equator

1. Dec 20, 2003

### greaser

I am trying to find what velocity and angle of launch is required for a projectile to be fired from the North pole and land somewhere on the equator. I was thinking 45 degrees with muzzle velocity 9401m/s but that sounds ridiculous. Also how much time would it be in the air for?

2. Dec 21, 2003

### HallsofIvy

Staff Emeritus
Looks to me like a very difficult problem, probably involving solving a nasty non-linear differential equation.

IF it were a matter of finding the angle and initial velocity of a flat plane, with constant gravitational acceleration, a distance equal to the distance from the north pole to the equator, then it would be relatively simple. However, if you REALLY mean "north pole to the equator" you will have take into account the curvature of the earth and the fact that you are firing the projectile around 1/4 of that curvature. Your trajectory will be high enough that you will have to take into account the fact that the gravitational force falls off as 1/r2.

3. Dec 21, 2003

### arcnets

I think this problem becomes simple if we may neglect air friction and any deviations of the earth's surface from being a sphere.
Because in this case, an orbit will do which is 'infinitesimally close' to a circular orbit. Which means: fire horizontally with circular orbit velocity.

I'm afraid we must *not* neglect those...