earn some best answer points.?

Question

this is a test for the yahoo community. if you drop a bullet from your hand at the same time as you shoot a bullet in a perfectly horizontal direction. they should hit the ground at the exact same time but they dont. the first one to tell me why it is that logically they should hit the ground together but dont in real life wins ten points.

Answer 1

if you drop a bullet while firing another bullet horizontally simultaneously then they should both hit level ground at exactly the same time. And yes they actually do in real life as long as nothing is in the way and the ground is level.

The reason WHY is because the force of gravity on earth is a constant. So both bullets fall toward the ground at the same rate. (the bullet fired horizontally moves faster and travels more distance but still loses altitude at the same rate of the bullet that you dropped from your hand)

So then both bullets should and will hit the ground at the same exact time.
The only reason why the bullet fired might not hit the ground at the same time is because there might be something in the way. Or the ground isn't level. Or you don't shoot the bullet exactly horizontally or you accidently put a little force on the bullet being dropped.

i've actually conducted this experiment using steel marbles and a machine designed for this exact experiment.

Answer 2

Hi Guy from britain

I think you're talking about earth curvature here, so let's see how significant it is. As my test gun, I'm going to select the M16A2 5.56mm Semiautomatic Rifle which has a muzzle velocity of 853m/s, firing an extremely aerodynamic round.

The bullet is fired locally tangential to the ground, which is assumed to be flat, curving only naturally. The initial height for firing will be 1.5m above the ground. From there, it takes 0.55 seconds for a falling bullet to hit the ground, meanwhile the fired bullet will have travelled 472m horizontally. Over this distance the earth will have curved enough so that the fired bullet has a further 17mm to fall. The end result is that the fired bullet will hit the ground 3 tenths of a millisecond (0.0003seconds) after the dropped bullet.

My money says you won't notice. :o)


Hope this helps!
The Chicken

Answer 3

i suppose i can try answering this, and hope that i am correct and no one has already answered this correctly.

first, they should hit the ground at the same time because gravity is constantly acting and acts equally on both bullets. there is a demonstration for beginning physics classes that has a projectile aimed at a stationary target. at the instant the projectile is projected, the target is released and allowed to fall. the projectile falls at an identical rate and hits the target.

second, since the earth is round, the ground is not perfectly flat, and the bullet that was fired horizontally actually has a greater distance to fall so takes longer to hit the ground.

Answer 4

guess what answer the teacher wants reason #1:
the ground is not perfectly flat. It is curved at a global level due to the Earth being round, and even more curved at a local level cos... well it just is.
As such if I extend out a line several hundred meters to where the bullet will land, the height from the ground is different there than it is here. hence different times to fall (fractionally so due to the global curvature, not so fractionally so due to the local curvature).

guess what answer the teacher wants reason #2:
guns have barrels.
Over the time it takes from when the bullet is shot to the time when it leaves the barrel the bullet is not actually falling due to gravity, hence will not land at the same time.

guess what answer the teacher wants reason #3:
rifling of the bullet is imperfect there being more drag exerted on the underside of the bullet as it drops. This drag gives a slight amount of lift to the bullet at the cost of it's horizontal velocity. This lift slightly reduces the rate of descent increasing the time taken for it to hit w.r.t. the one dropped from the hand. hence they don't hit at the same time.

guess what answer the teacher wants reason #4:
recoil of the gun causes deflection of the bullets path off the horizontal while it is still in the barrel. Most sharpshooters learn to compensate for this. It is one of the techniques you learn to master. Bullets will hit at different times but i think we can rule out this reason as we'll assume a measure of expertise on behalf of the shooter.

edit: oh wait.. you're from Britain maybe this is meant to be a joke... always did like British humour... let's see Britain, Britain, Britain,...
maybe it's the weather, the London smog might dissolve the bullet before it hit the ground. surf at the beach being measured in inches rather than feet? no that wouldn't do it.

Hang on I got it!
Why would your hand be at the same height as where you'd fire a gun from? Who keeps their hands at shoulder height? Of course it'd be much closer to the ground so it'd hit first.

Answer 5

There is only one reason why they might not fall at the same time. If you literally FIRE the bullet at the same time as the other one is dropped, then the fired bullet has a split-second reprieve from gravity until it clears the barrel of the gun.

If you dropped the held bullet at the exact same time as the fired bullet left the barrel of the gun (AFTER it was fired), then there would be no difference. But it would take some pretty crackerjack timing.

Answer 6

They should hit the ground at the same time because they are being dropped at the same heigth. The reason that they don't land at the same time is because of the friction between the air and the bullet in which drops from your hand while the other is getting the advantage from having a mechanical object to make it go faster-less friction.

Answer 7

Because we are not living in a gravity free region. And it is all not same horizontally and vertically, horizontally the bullet will be attracted by the gravity in a curved path (because of down forward motion), while vertically it may adopt a straight line.
So the vertical one will hit the ground first.

Answer 8

The bullet fired from the gun encounters air resistance a lot more than the other bullet. Also it cannot exceed the terminal velocity when coming back down. Therefore the bullet from the gun takes more time.

Answer 9

you gotta believe in the power of the guns...
guns can do anything, even defy the laws of physics
that's why