If You Are Moving at the Speed of a Bullet and Shoot It Backwards, What Happens?

Photo by Niels Noordhoek / Wikimedia Commons / CC-BY-SA 3.0

Let’s say that you are traveling along at about 300 km/h. For some reason, you decide to do some target shooting in order to pass the time. So you take out your trusty gun, or cannon, or what-have-you, and you point it backwards. In this case, you are firing in the opposite direction that you are traveling (after all, you don’t want to shoot the pilot). As luck would have it, your weapon fires at the exact same speed that you are traveling. So, you are flying along at 300 km/h and you are about to shoot a bullet/cannon/whatever in the opposite direction at 300 km/h.

What happens to the projectile? Does it go shooting off in the opposite direction? Does it go anywhere? It may seem like a silly question, but it is important to any aft firing aircrafts.
There are a few different answers to this question, depending on the specific conditions; however, the short answer is:

–You are traveling along a path at 300 km/h. We will call this “B”

–You fire in the opposite direction at 300 km/h. We will call this “-B”

–So you are traveling at B and you fire at –B

–And –B + B = 0, so the bullet should fall straight down. That’s right; you pull the trigger, the projectile plummets straight down.

What would this look like? For an onlooker, someone who is standing still and watching you fly by, they will see you take aim and pull the trigger; however, the bullet leaving the weapon will appear to fall straight down as the plane pulls away from around it (I am assuming that the back of the plane is open, and that the observer has windows to see all of this happen).

However, in reality, things are a bit more complicated. First, even if the projectile can travel 300 km/h in the opposite direction, it will need a bit of time to reach that speed. In short, when you pull the trigger, the bullet won’t immediately be traveling at 300km/h in the opposite direction (-B). Since the bullet takes time to accelerate, when you pull the trigger, the bullet in the chamber will have to speed up to reach –B and cancel out the effects of B.

So in reality, the projectile would not fall straight down; it would a short distance after the point at which you shot it.

The short answer also assumes that there is no air resistance. And of course, there will be air resistance. Also, in a gun, rifle, or similar weapon, the projectile will spin. Both the air resistance and spin will cause the projectile to go off course a bit. In other words, it won’t go back perfectly straight, and will end up shooting off course a bit (which means no falling straight down).

That said, assuming that you give up the whole target shooting idea and just want the projectile to fall straight down, it is *possible* to get the projectile to do this – it is just exceedingly hard as the conditions have to be nearly perfect. Unfortunately, I don’t have the time to establish perfect conditions…but others did. To see this in action, check out the MythBusters video.

Along these same lines, if you shoot forward at 300 km/h, then the projectile will be moving forward at 600 km/h relative to the ground (again, this is not taking any contributing factors into consideration)

Video>>https://www.youtube.com/watch?v=BLuI118nhzc

Source:- quarksandquasars.com