If you are traveling at 100 MPH and have a gun that shoots bullets at 100 MPH

[Jeff7]

Originally posted by: nkgreen
But if you going forward at the speed of light and shoot a bullet forward at the speed what happens then? Riddle me that!!

It moves at the speed of light too, relative to you. But since you're going fast, time slows down for you, so it still looks like it's moving at the normal speed of light, even though it's going the same speed as light in the rest of the Universe - relative to you, it's not moving very fast.
General relativity is fun.

Originally posted by: DT4K
The lack of basic physics knowledge(or even common sense) on this forum is quite stunning.

NO, it will NOT appear to be going 200mph from the perspective of the shooter. The gun has a muzzle velocity of 100 mph. It's not going to double just because you are moving backwards. The bullet will appear to be going 100 mph from the perspective of the shooter, which means it's going 0 mph from the perspective of the ground. It's really as simple as:

100 + (-100) = 0

In my physics class, plenty of people seemed to have trouble with this:
If you throw something upwards, when it reaches its peak, what is its vertical velocity?

The vertical velocity is zero, since it's neither moving up nor down. The fun part is then asking what its acceleration is at that moment.

Answer: 9.81 m/sec^2. As long as you're on Earth around sea level and in freefall, you're experiencing an acceleration of 9.81m/sec^2. The ball thrown up is in freefall both ways, and so is subject to gravity's acceleration.

 

[TXHokie]

Now we know who was sleeping in the back of physics class...lol.

 

[Whisper]

Originally posted by: DT4K
The lack of basic physics knowledge(or even common sense) on this forum is quite stunning.

NO, it will NOT appear to be going 200mph from the perspective of the shooter. The gun has a muzzle velocity of 100 mph. It's not going to double just because you are moving backwards. The bullet will appear to be going 100 mph from the perspective of the shooter, which means it's going 0 mph from the perspective of the ground. It's really as simple as:

100 + (-100) = 0

See, that's the explanation that made the most sense to me when I was trying to think of all this in terms of vectors. Then again, all I remember about vectors from high school is drawing them on graph paper, and thinking how much it sucked.

 

[mooncancook]

Originally posted by: DT4K
The lack of basic physics knowledge(or even common sense) on this forum is quite stunning.

NO, it will NOT appear to be going 200mph from the perspective of the shooter. The gun has a muzzle velocity of 100 mph. It's not going to double just because you are moving backwards. The bullet will appear to be going 100 mph from the perspective of the shooter, which means it's going 0 mph from the perspective of the ground. It's really as simple as:

100 + (-100) = 0

I would disagree.
First you cannot fire a gun and have a bullet traveling at 100mph.
The initial speed of the bullet is 0, so right when the bullet is fired, the bullet is traveling at velocity of -100 by a stationary observer. The bullet then travels at an acceleration of a=f/m, which depends on the initial force. So until the bullet reaches velocity of 100, it would have travel at negative decelerating speed. When it reaches 100 relative to the gun, and let's ignore drags and winds, the bullet will look stationary to the observer, but it would have travel a small negative distance from the observer's POV. The negative distance depends on the time for the bullet to reach 100mph relative to the gun.

 

[Furyline]

I just did some experiments by running back and forth and throwing a ball, and based on that, I think it would drop to the ground

 

[torpid]

Originally posted by: Born2bwire

Originally posted by: torpid
Would the bullet just stop in the chamber? I'm not sure how guns work, does it get to 100 mph only as it exits the chamber or before?

Technically, it would be accelerated along the barrel until it exited the muzzle of the rifle and here we are assuming the muzzle velocity is 100 mph. From the frame of reference of the shooter, the bullet will still travel out at 100 mph, only from those that are at rest on the ground will the bullet have no horizontal velocity. Basically, from the ground reference, I would picture the bullet moving along in the barrel with the car and when fired, slowly decellerating up to a standstill when it leaves the barrel.

I was thinking more along the lines of, a bullet fired at 100mph might lose much of its velocity inside the gun itself because it's not going quickly enough and thus might drag against the bottom of the gun as it exits.

 

[50cent1228]

nope ur wrong

 

[OVerLoRDI]

Originally posted by: cjchaps
Let's say you are traveling at 100 MPH in a forward direction and have a gun that shoots bullets at 100 MPH. If you aim it backwards and fire does the bullet drop straight down? I assume the answer is yes but I'm not 100% positive....

Yes, it falls straight down to the ground.. the ground being what isn't moving. You would still be moving away from the bullet at 100mph but reference to the ground the bullet is not moving.

 

[jupiter57]

Originally posted by: cjchaps
Let's say you are traveling at 100 MPH in a forward direction and have a gun that shoots bullets at 100 MPH. If you aim it backwards and fire does the bullet drop straight down? I assume the answer is yes but I'm not 100% positive....

Oh definitely YES!
Just like the plane that takes off without any lift on the wings, BUT: the engines are running!!!

 

[randay]

Originally posted by: Furyline
I just did some experiments by running back and forth and throwing a ball, and based on that, I think it would drop to the ground

ARE YOU MAD?!?! STOP TEARING HOLES IN THE SPACE/TIME CONTINUUM!!!

 

[mooncancook]

Originally posted by: OVerLoRDI

Originally posted by: cjchaps
Let's say you are traveling at 100 MPH in a forward direction and have a gun that shoots bullets at 100 MPH. If you aim it backwards and fire does the bullet drop straight down? I assume the answer is yes but I'm not 100% positive....

Yes, it falls straight down to the ground.. the ground being what isn't moving. You would still be moving away from the bullet at 100mph but reference to the ground the bullet is not moving.

It will not fall straight to ground in reality because no gun fires at 100mph. The bullet must be fire at initial speed of 0 mph and accelerate to its terminal velocity and decelerate until it reaches speed of 0 again. The bullet will have a variable speed relative to ground observer due to force/acceleration at play.

 

[maximus maximus]

Originally posted by: cjchaps
OK, that is what I was thinking.

Originally posted by: Tom
someone not in the car would see the bullet drop straight down. If you're in the car, the car isn't moving relative to you, the bullet would go south away from you at 100 mph.

 

[mrSHEiK124]

Does that mean that when I'm doing 80 MPH on the highway, the light from my tail lights is actually traveling at the speed of light minus 80 MPH?

 

[torpid]

Originally posted by: mrSHEiK124
Does that mean that when I'm doing 80 MPH on the highway, the light from my tail lights is actually traveling at the speed of light minus 80 MPH?

No, because electromagnetism does not behave the same way as physical objects. Theory of Special Relativity, etc.

 

[JEDI]

Originally posted by: cjchaps
Let's say you are traveling at 100 MPH in a forward direction and have a gun that shoots bullets at 100 MPH. If you aim it backwards and fire does the bullet drop straight down? I assume the answer is yes but I'm not 100% positive....

100-100 = 0 mph

yes

 

[bersl2]

Originally posted by: torpid

Originally posted by: mrSHEiK124
Does that mean that when I'm doing 80 MPH on the highway, the light from my tail lights is actually traveling at the speed of light minus 80 MPH?

No, because electromagnetism does not behave the same way as physical objects. Theory of Special Relativity, etc.

Never mind, I'm an idiot.

 

[DT4K]

Originally posted by: mooncancook

Originally posted by: DT4K
The lack of basic physics knowledge(or even common sense) on this forum is quite stunning.

NO, it will NOT appear to be going 200mph from the perspective of the shooter. The gun has a muzzle velocity of 100 mph. It's not going to double just because you are moving backwards. The bullet will appear to be going 100 mph from the perspective of the shooter, which means it's going 0 mph from the perspective of the ground. It's really as simple as:

100 + (-100) = 0

I would disagree.
First you cannot fire a gun and have a bullet traveling at 100mph.
The initial speed of the bullet is 0, so right when the bullet is fired, the bullet is traveling at velocity of -100 by a stationary observer. The bullet then travels at an acceleration of a=f/m, which depends on the initial force. So until the bullet reaches velocity of 100, it would have travel at negative decelerating speed. When it reaches 100 relative to the gun, and let's ignore drags and winds, the bullet will look stationary to the observer, but it would have travel a small negative distance from the observer's POV. The negative distance depends on the time for the bullet to reach 100mph relative to the gun.

What are you disagreeing with? It sounds to me like you agree in general, but you are adding more detail. Yes, it will be moving relative to the ground until it reaches that 100mph velocity (in relation to the gun).
But as with all physics problems, some level of simplification is required to come up with a reasonable approximation of what would happen. In this case, I was simplifying by ignoring what happens in the few microseconds between the time the bullet is struck and the time it exits the barrel. If it exits the barrel with a muzzle velocity of exactly 100 mph, it will fall straight to the ground (again ignoring details like the air movement that is created by the moving vehicle) Besides, during the time it is accelerating (or should we say accelerating negatively), the barrel prevents it from having any vertical velocity. So as soon as it exits the barrel, yes, it drops to the ground.

Plus, the observer can't see it when it's in the barrel anyway, so the only thing that matters is what happens after it exits the barrel.

 

[cubby1223]

Originally posted by: nkgreen
But if you going forward at the speed of light and shoot a bullet forward at the speed what happens then? Riddle me that!!

Bullet doesn't fire out of the gun. As you approach the speed of light, your mass approaches infinity. Thus it would take an infinate amount of force to accellerate anything that's already travelling the speed of light. The gun powder will have no affect on the bullet.

 

[yowolabi]

Originally posted by: mooncancook
So if I'm traveling on a train at 100mph, and I throw a rock backward at 10mph, the rock is going to come back and hit me at 90mph. I'll be damned.

This is the first thing that had me literally laughing out loud in a long time.

 

[jupiter57]

Originally posted by: jbourne77
You bought a POS gun, my friend.

ROFLOL!

 

[jupiter57]

Originally posted by: hanoverphist

Originally posted by: GuitarDaddy
Pie r round
Cornbread r square

cornbread muffins are round

All my cornbread is round!
Iron skillet cornbread FTW!

 

[thescreensavers]

Originally posted by: Tom
to someone not in the car the bullet would appear stationary. If you're in the car, the car isn't moving relative to you, the bullet would go south away from you at 100 mph.

this is what I think

 

[ballmode]

OP needs school