Shooting up/down slopes

Ok i heard somewhere that if you shoot a weapon uphill, its vertical component dissipates quicker due to gravity and the bullet goes just below where you aimed.

And the reverse for downhill, the bullet overshoots the target.

Is this true? and if so, how does it work?

 

Yes its true! It depends on the angle so that you may shoot at 100yards and for an 42° angle the real distance is around 78yards. So you always have to aim a little deeper for an angle shot.

Regards

Ulrich

 

Yes, it is true for the following reason. Gravity, or the effects thereof on the projectile.

Think of it this way,.... you can throw a ball farther downhill than you can uphill because as it flys downhill your ball (projectile) is assisted by gravity, and just the opposite occurs when throwing it uphill.

Said another way, if you can throw a ball 100 yards across a flat surface, then using the same force it will go more than 100 yards if you are throwing downhill, and less than 100 yards if you are throwing uphill.

So if your weapon is sighted in at a distance of 100 yards on a level surface, the projectile will experience the same effects as the ball if you hold directly on target firing uphill and downhill respectively.

Duckbill

 

Not entirely true. A ball isn't the best example as it rolls when it lands so technically throwing a ball uphill could make it 'land' somewhere behind you down the hill.

Also, Gravity doesn't increase - the pull of Gravity remains at a constant level, and air resistance also takes effect on the bullet. If you were to shoot a bullet parallel to the ground, it would hit the ground at the exact same time as a bullet that you drop from equal height.

A bullet arcs when it is fired, so shooting a target 'uphill' from you requires you to aim hire to compensate for the arc.

 

Mussolini,

My attempt at simplifying a rather complex issue was unsuccessful. Your reference to "arc" was a much better way of putting it.

The Point of Impact of the projectile (ball) is implicit in the discussion. Rolling was not mentioned, nor does it factor into the discussion topic.

Gravity is, as you say, a constant. No one has suggested that gravity is not, for the purposes of this discussion, a constant.

Gravity, air resistance, and drift are among the factors affecting the flight of a projectile (trajectory). The trajectory of a projectile is the result of these factors, with the effects of gravity on the mass of the projectile being the only constant.

The Angle of Site (not sight) that is relevant to this discussion. (“Site” refers to the site survey of the gun position relative to the altitude of the target.) If the target is above or below the gun, the range-table angle must be increased or decreased, as the case may be, by the angle between a horizontal plane through the gun muzzle and the line gun-muzzle target. This latter angle is called the Angle of Site. (Bishop, Field Artillery, p. 95.)

(The terminology used in this post is consistent with that employed by the US Army Field Artillery during WWII.)

I hope this clarifies the matter somewhat.

Duckbill

 

Aim High 1 minute of angle high for every 100 yards up hill for less than 45 degrees and 1 minute of angle low for shooting down hill less than 45 drgrees. Thats just a general rule depending on the type of round and weapon you are using.

You have to treat gravity like wind value.

 

http://www.google.co.uk/imgres?imgurl=http://www.chuckhawks.com/bullet_trajectory2.jpg&imgrefurl=http://www.chuckhawks.com/bullet_trajectory.htm&h=212&w=550&sz=32&tbnid=vGXmrjLgbMoF4M:&tbnh=51&tbnw=133&prev=/images%3Fq%3Dbullet%2Btrajectory&hl=en&usg=__hjiwftkBlS4_WUhBj3rDHLok-OM=&sa=X&ei=_TIsTJaXIZPw0gS2ufC2CQ&ved=0CDIQ9QEwBQ shooting uphill, downhill..

Google Image Result for http://image.absoluteastronomy.com/images/encyclopediaimages/t/ta/targetshooting3.gif

this goes some way in answering question..

 

Mussolini,

When I woke up this morning I realized that what I had written previously(above) reads very much in the manner you suggested. That is to say, I implied that gravity was not constant.

My apologies for the confusion. I chose a very clumsy way to express myself.

Duckbill

 

this link describes it well.. Topic of the Month

 

The thing about gravity is about the one thing I remember from physics - an elephant doesn't fall out of a plane any faster then a human, the mass of the object and aerodynamics is what makes the Elephant hit the ground first.

In a 'perfect' setting, the Elephant and human would land at the same time as they both fall at the same rate (I think gravity pulls with a 10.5 ft per second force or some such?).

I think I also slightly misread the OP (I interpreted him as saying that gravity pulls more on the bullet when you shoot it uphill) but I think the answers in this thread have sufficiently answered the OP question.

 

That would be in a vacuum such as space, it is what allows astronauts to work outside of the vehicles.

 

Yep - no wind resistance or anything...its been a while since I was in HS...so yes, in a vacuum with the gravity of earth, two objects no matter what their size, shape, mass, would land at the same time if dropped from the same height at the same time.

 

True, gravity as a constant was demonstrated on one of the moon landings (forget the number) when an astronaut dropped a feather and a hammer from the same distance, at the same time, and they both struck the surface of the moon at the same moment.

Here is the YouTube of that experiment for anyone who hasn't seen it.

Goto:

http://www.youtube.com/watch?v=WOvwwO-l4ps

 

Here is a link BTW which really explains ballisitic trajectory in "layman's" terms which makes it much easier to visualize.

Goto:

Bullet Trajectory

 

touche clint. my post too...

 

I am sure that wasn't Armstrong on 11, but one of the later landings. I'll have to see if I can find the number (15?). But I know it wasn't Armstrong.