physics question

[onedash]

I got one.
You have a rifle with the barrel parallel to the ground. when you fire it an identical bullet is dropped next to and at the same height of the barrel at the exact instant the fired bullet leaves the barrel.
which one will hit the ground first?

And here is another one right away...
If you are on the bottom of a mountain and you see a deer that you estimate the range to be 500 meters with a range finder or map (or any accurate method). The ground is on a 45 degree angle. Will your 500 meter setting allow you to hit the deer? Never mind windage.
The same answer applies if you are at the top looking down...

[michael.scheller]

1. Exactly the same time.

2. You'll shoot high. Same thing would happen if you were to reverse the position of the deer and the shooter.

[gjat]

1- The dropped bullet would hit the ground first. The fired bullet was given energy to propel the bullet perpendicular to the force of gravity and would not fall at the same rate as an object with no other source of energy.

2- Depends upon the 'load' of the shell. How much powder was used to provide energy tothe bullet when it is fired. A high load bullet should have enough energy, a low load bullet may not. You'd have to know the load characteristics of the shell to calculate the trajectory of the bullet.

[JBCrooks]

1) They hit the ground at the same time. The fired bullet has its energy applied at a right angle to the force of gravity, the two forces do not oppose, so gravity pulls down the fired round at the same rate as the dropped one.

2) The 500yd setting on the rifle would cause the round to fall far short when shooting uphill since gravity would be working against the forward movement of the round. Shooting downhill would be opposite. The round would overshoot the target.

[onedash]

for number 2 apply this...you are on a building 500 yards tall. if you are looking over the edge and there is a target straight down next to the wall would you use a 500 yard dope or zero?

Gjat...assuming the same round is used when the rifle was sighted in at 500 yards on a range. It is less a question about trajectory and more a geometry (not physics) Picture a triangle....

[Daryl]

They would hit the ground at the same time.
When firing up hill or down hill the bullet will hit higher than it would over a horizontal course.

[Stytooner]

I may be wrong on this one, but I've heard the bullets will hit at the same time, however the airplane question could come into play here too I think. Standard bullets may surely act like this but what if you used non standard shaped objects.

Drop an airplane 10 foot from the ground or shoot one out straight ahead 10 foot off the ground. The one you dropped will hit first because the other will glide some. I don't think bullets glide out of the box, but maybe you can see my point.

The 500 yard setting will work fine if you are using a powerful enough round. You have the sights set for 500 yards already. It better hit the target or you better go zero it in again.
I think the farthest I have shot without a scope was 300 yards in basic. I hit the targets at 300. Some were even higher than others.
If the scope is set for 500, it will go there if you are using it whether shooting up or downhill.

[LCHIEN]

I got one.
You have a rifle with the barrel parallel to the ground. when you fire it an identical bullet is dropped next to and at the same height of the barrel at the exact instant the fired bullet leaves the barrel.
which one will hit the ground first?

This is a trick question.
Assuming the barrel is parallel to the ground, the vertical component of velocity will be the same no matter what the horizontal velocity, so they will hit the ground at the same time,

BUT, in truth, there really is no parallel to the ground, only tangential at that point since the earth's surface is a spherical surface. If the barrel were tangential to the surface, then the ground falls away in all directions, thus, the bullet dropped will hit the ground first, the bullet fired will have a longer distance downward to travel. The earths curvature is very slight due to the large diameter, the time difference will be very, very small, but finite.

And here is another one right away...
If you are on the bottom of a mountain and you see a deer that you estimate the range to be 500 meters with a range finder or map (or any accurate method). The ground is on a 45 degree angle. Will your 500 meter setting allow you to hit the deer? Never mind windage.
The same answer applies if you are at the top looking down...

It (elevation compensation for distance) won't work quite right, the elevation has to do with the gravity-induced vertical droop of the bullet. If you fire straight up there will be no droop. If you fire at 45° the droop will be .707 of what it is compared to fully horizontal, so your shot will be slightly high.

The bullet (fired uphill) will slow down a little and be in the air longer and perhaps droop some more (compensating somewhat) and a bullet fired down will will have a partial gravity assist speeding up (or at least not slowing down as much as one fired horizontally) with a little less droop, increasing the error.

BUT, in truth we're only talking a matter of small inches compensated droop so
you'll still hit the deer which is a target on the order of feet.

[Hellrazor]

Bullets will hit at the same time.

Your bullet will impact almost the same spot. Your real problem is properly targeting the animal since the trajectory through the animal will be different then shooting on a flat plane.

[Black wallnut]

#1 they will hit at the same time.

#2 You will shoot high, likely over the deers back. Gravity has an effect on the horizontal plane. To judge bullet drop you need to figure the horizontal distance to target. Beyond 300 yards bullets have lost much of their velocity which is one important factor in drop. 500 yards at 45° = about 350 horizontal yards.

Just for fun lets look at the trajectory table for what I use for elk. .338 winchester magnum with a 225 grain bullet with a muzzle velocity of 2900 fps. If I use a Speer boattail bullet with a ballistic coefficient of .484 that bullet will lose 1000fps at 500 yards and with a 300 yard zero will be at -29.8" (below line of sight) at 500 yards. 11.2" below at 400. So past 300 yards exact horizontal distance to target is critical to correct shot placement.

Hellrazor brings up an interesting point which is the path the bullet must take at a 45° angle in order to hit the kill zone of a deer. The classic both lung shot is darn near impossible!

[gjat]

for number 2 apply this...you are on a building 500 yards tall. if you are looking over the edge and there is a target straight down next to the wall would you use a 500 yard dope or zero?

Gjat...assuming the same round is used when the rifle was sighted in at 500 yards on a range. It is less a question about trajectory and more a geometry (not physics) Picture a triangle....

I'm convinced it is a matter of trajectory. Remember, an object in motion will stay in motion unless acted on by another force. The fired bullet has the energy imparted to it from the chemical explosion. Then it is acted upon by wind and gravity. wind drag and gravity needs time to overcome the energy imparted by the firing. The dropped bullet is acellerated by gravity alone (32' per second) gravity does not have to have time to overcome the motion energy imparted by the chemical explosion.

[JBCrooks]

Basic 500yd zero for a rifle on a range: Picture a line straight between they eye, the rear sight, the front sight, and the target. When a round is fired, the projectile leaves the barrel some distance below this line (around 2" on an M16A2), rises across the line at around 30yds (the relationship between the sights holds the barrel at an upward angle when shooting along a flat line), peaks out at roughly the midway point a few yards above the line, and falls back into the line at the 500yd point to hit the target.

If you fire with that setting at a 45degree downhill slope, you will only have about 1/2 the drop of the round in that distance. The round will pass roughly 1.5-2 yards above the back of the deer.

It is very surprising how much a bullet in flight can be affected. At the 500yd line, a 10mph crosswind will move the strike of the round about 11ft sideways if not compensated for.

[onedash]

Black Walnut has the best answer...If the speed of the bullet remained unchanged we would have super flat shooting bullets and range estimation wouldn't be very important. And if there was no gravity we could always just aim somewhere and always hit 2 inches (distance of sights above the bore) below.
But if the elevation used to normally hit the taget at 500 yards(remembering that a 1 MOA rifle will print a 5" group) was used to hit a target that was on a steep hill you need to use the elevation setting for the horizontal distance to the target (base) not the line of sight range (hypotonuse) And yes a range mis-estimation that great will more than likely mean you are going to miss by shooting over the target....
Now if you guess 250 and its only 150 you could still be within 1-3 inches depending on caliber...
Some intersting facts.
Higher temp, higher humidty, higher elevation should make you a better shooter ballistically speaking. I prefer to shoot in colder weather though because more cloths means more cusion and I hate the heat. As long as your not shivering and no heat waves distorting the target....

I got a remington 700P in 300 Remington Ultra Mag and I really need to start practicing......It should easily be a 1000 yard rifle...bullets are $2 a piece..So once I start I want to reload...
But that would really dig into the wood working right now....

[Crash2510]

1.) the bullets when disregarding friction etc will hit the ground at the same time because when figuring time to hit the ground you figure in only the vertical y components of the acceleration vector

to figure how long it takes to hit the ground you only use gravity

2.) if you are shooting uphill the bullet will fall short/low because it has to overcome gravity which takes more force