How fast does a bullet shot at a 90 degree angle hit the ground?

Answer 1

It is a common belief that a bullet fired at a 90 degree angle, perpendicular with the ground, will impact the surface simultaneously with a bullet dropped at the same altitude of the muzzle of the gun firing the projectile.

However, this theory cannot be confirmed due to several exterior ballistic variables such as ambient air density (temperature and humidity), air resistance, wind, Coriolis effect, Eotvos effect, and the ballistic coefficient of the projectile.

With all of these variables excluded, there is one thing that still disproves this common misconception.. That being the Magnus Effect.

Magnus Effect

The phenomenon whereby a spinning object in the course of a forward vector is acted upon by a perpendicular force caused by the object moving through a liquid or gas.

When a bullet is fired, the rifling in the barrel causes the projectile to spin in a clockwise motion (in most guns), this causes the bullet to veer from its forward vector due to water in the air (humidity).

Without wind, this phenomenon causes the bullet to rise and move to the right. This effect is very important to marksman because wind can force the projectile to ^roll^ or drop- a bullet subject to a downward-left force due to wind hitting the right side of the bullet.

This effect can be accurately predicted based on the rifle's turn rate, which can increase or decrease the effect because various rifles are made to fire with a turn rate of either 1:9 or 1:12, meaning the bullet will complete a revolution once every 9 inches, or 12.

Answer 2

A bullet shot straight up at a 90-degree angle will lose its forward velocity and only be affected by gravity. It will then fall back down to the ground at the same speed it was shot, making it hit the ground at the same speed it was initially fired, typically around 300-400 meters per second for handguns.