got thinking last night

well i was in bed last night and i just got thinking about a wierd thing that would probly never happen in real life but i would like to know if anyone has an answer. well here goes.

if a bullet was shot at a car and both objects were traveling at almost exactly the same speed, just the car is going slightly slower would the bullet end up breaking the glass? im talking about in the perfect worls, both objects remain at a constant speed. i just didnt know if the bullet would just hit the window and bounce off or if it would go through the window.

im assuming you mean in the same direction, also how much slightly slower?

Einstien special relativity would suggest that the bullet is moveing at a speed in relatiion to the speed of the car or vis versa.

(mps= meters per second)
lets say the bullet is traveling at 1000mps in relation to the ground

now lets say that the car is moving 999mps in relation to the ground

so the bullet is traveling 1mps in relation to the car, 1mps may be enough to yield a break in the windshield.

however as i see this experiment , as the bullet traveling through the backwindow(removed of course) travelling through the passenger areas and comin in contact with the windshield, id perdict deflection due to the angle of the windshield.

Originally posted by caspiantiger
if a bullet was shot at a car and both objects were traveling at almost exactly the same speed, just the car is going slightly slower would the bullet end up breaking the glass? im talking about in the perfect worls, both objects remain at a constant speed. i just didnt know if the bullet would just hit the window and bounce off or if it would go through the window.

Yes. This relative velocity is a basic of Newtonian physics as well as more advanced models.

If you take physics lab courses at some point you even do this in many forms (though not gun/car because no cars go that fast).

An easy way to see a similar thing is tossing around an uncooked egg. Notice when you catch it, you move your hands back as it comes in. This is the same effect, slowing down the relative speed to ease the stress on the egg. If you just hold you hand still, it will probably break when you catch it.

Yeah, they beat me to it.

It would depend on how much slower the car is traveling.

If you take the bullets speed, minus the cars speed, you get the speed the bullet is to impact the window at. It is at that speed that you need to determine wether the bullet can break glass.

If its the same speed you can toss it yourself, chances are it's not going to break the glass.

Now if the car is heading toward you, and you fire that bullet, the bullet will be able to pierce through more than it would if the car were sitting still.

Ok thanks guys, that really clears it up for me. I dont get to take college level physics until fall of next year. i have one more thing that kind of puzzles me. I understand the whole speed relative to the car thing, but heres my question.
Say your in a school bus for example. and you have an RC helicoptor. The helli is stationary on the floor of the bus moving 0MPH relative to the bus, but moving 50MPH relative to the ground (bus is going 50) if i flew the helicoptor up in the air and let it hover with no thrust in any direction but up and down would the heli eventually start moving towards the back of the bus? would it matter weather the windows were down or not? (neglecting wind) like i dont know if the windows were up the air in the bus would be considered going 50mph relative to the ground so the heli would stay still, or if with the windows open it would be considered the air was 0mph relative to the ground and th heli would take off to the back of the bus.

thanks again guys/

Originally posted by caspiantiger
Ok thanks guys, that really clears it up for me. I dont get to take college level physics until fall of next year. i have one more thing that kind of puzzles me. I understand the whole speed relative to the car thing, but heres my question.
Say your in a school bus for example. and you have an RC helicoptor. The helli is stationary on the floor of the bus moving 0MPH relative to the bus, but moving 50MPH relative to the ground (bus is going 50) if i flew the helicoptor up in the air and let it hover with no thrust in any direction but up and down would the heli eventually start moving towards the back of the bus? would it matter weather the windows were down or not? (neglecting wind) like i dont know if the windows were up the air in the bus would be considered going 50mph relative to the ground so the heli would stay still, or if with the windows open it would be considered the air was 0mph relative to the ground and th heli would take off to the back of the bus.

thanks again guys/

The Helicopter would continue to operate normally--as though from the ground. Another matter of Newton's Laws. All of this is true provided all other factors remain equal--no wind, etc.

Interestingly, given any moving vehicles, all objects in the vehicle are, of course, traveling at the same velocity. Therefore, should you stand from your position and move toward the front of the bus, your progress would mean that you are moving slightly faster than the floor. To the rear, slightly slower, relative to the FORWARD motion.

Again, according to the Second Theory of Relativity; relative to a point of stasis (control point or "observer"), those persons on the bus, traveling 50 miles per hour for 30 minutes will age less during that time segment than the observer will. Time is a function of motion. As velocity increases--eg, the speed of light is approached, Time slows down relative to the observer. IOW-- "moving Clocks go slow".

Physics is a completely facinating subject.

a simple way to understand these types of experiments is to quantify your varibles within your tests.

what i mean is you start with the fiction zero(a perfectly controlled environment),then add any/all other elements to the equation(ie. gravity ,velocity, viscosity, measure of mass,ect...). then determine how they effect each other in relation to one another. at that point you will have the backdrop to find your solution.

that may seem daunting but its actually quite simple. you can find answers to your questions and not need the help of others(reliance is an obstruction). its much better to find things out yourself than have to take someones word for it.

Originally posted by Ed Littlefox
Physics is a completely facinating subject.

it truly is, and i wish you luck caspiantiger in your progress into physics

Originally posted by Ed Littlefox
The Helicopter would continue to operate normally--as though from the ground

Aslong as the bus is moving in uniform motion. If the bus was to accelerate suddenly the helicopter would move towards the back.

Originally posted by Ed Littlefox
IOW-- "moving Clocks go slow"

Meaningless statement all motion is relative saying the clock is just "moving" is meaningless. If someone went by in a car with a clock and said this clock is moving. The observer outside the car has just as much right to say no I am moving and you are stationary. You could say clock moving relative to earth experiance slower time. Also stating that the clock is slow is implying something is wrong with the clock. The clock is correct and there is nothing wierd or wrong with the clock it is time itself that it slower relative to earth.

[edit on 25-12-2006 by User0073]

Originally posted by User0073

Originally posted by Ed Littlefox
The Helicopter would continue to operate normally--as though from the ground

Aslong as the bus is moving in uniform motion. If the bus was to accelerate suddenly the helicopter would move towards the back.

Originally posted by Ed Littlefox
IOW-- "moving Clocks go slow"

Meaningless statement all motion is relative saying the clock is just "moving" is meaningless. If someone went by in a car with a clock and said this clock is moving. The observer outside the car has just as much right to say no I am moving and you are stationary. You could say clock moving relative to earth experiance slower time. Also stating that the clock is slow is implying something is wrong with the clock. The clock is correct and there is nothing wierd or wrong with the clock it is time itself that it slower relative to earth.

[edit on 25-12-2006 by User0073]

Hi--

The "given" here is that the bus DOES move forward with no change in velocity. You cannot rightfully insert a parameter that does not exist in order to refute what I said. We are talking "no random variables" here--such as acceleration or sudden stops.

The phrase, "moving clocks go slow" is one used by Stephen Hawking and other Theoretical Physicists when explaining Time as a function of Motion in the Second Theory of Relativity, to the common man and students. I understand it perfectly, and so do a lot of others, as it states that time passes more slowly when one is in motion than it does in a static state--relative to both the observer AND the subject.

Please, lets not insert random variables not given in the original question in order to support an entirely different, and unrelated, argument.

[edit on 26-12-2006 by Ed Littlefox]

I know what the statement means but it is a common incorrect statement. The meaning behind the statement is correct but the way the statement represents it is wrong.

user0073 tho your point is a valid point, Ed Littlefox is more accurate.

caspiantiger per posed a zero speed differance situation, as if the bus wasnt moving at all, becuase the heli was with same speed. as pointed out if the windows were to be open the result would change, becuase a new variable would be introduced "wind shear". and becuase the heli depends on varibles of drag, lift , and other air born anomalies, it trajectory would change.

Originally posted by User0073
I know what the statement means but it is a common incorrect statement. The meaning behind the statement is correct but the way the statement represents it is wrong.

Well-- quite frankly, I don't like the choice of phrase, either, but because it is used by the physicists that coined it, we are sort of stuck with it until they learn better English.

A footnote here, which may back the phrase, it's use, and the reason it was coined. That Time slows Relative to a static point has actually been proven. Several years ago, a portable Cesium Clock, calibrated against the Cesium Clock at the Naval Observatory in NY, was placed aboard a Transcontinental jet cargo flight to Heathrow in the UK. The clock on the plane lost 83 nsec. when checked against the N/O clock after landing. So, the airborn clock "went slow", as they would, and do, say in the UK.
That experiment has been repeated several times with like results, both on the planet and in space, and even compared, in orbit, against an atomic clock on board the Hubble ST.

oops sry, accidental post.

[edit on 27/12/2006 by ANOK]

ok this ones still kinda confusing me, let me restate it in other terms. Sya there is an enclosed box moving at 30MPH in a northward direction. If an boject that was resting on the floor (not necisarily a heli) would happen to rise from the floor of the box and stay at that hight elative to the floor of the box with no added horizontal velocity would the object eventually move south. The reason i ask this is because the object s no longer in contact with the box so i thought that after a period of time the object would start to decelerate and end up at the back of the box.

Originally posted by caspiantiger
ok this ones still kinda confusing me, let me restate it in other terms. Sya there is an enclosed box moving at 30MPH in a northward direction. If an boject that was resting on the floor (not necisarily a heli) would happen to rise from the floor of the box and stay at that hight elative to the floor of the box with no added horizontal velocity would the object eventually move south. The reason i ask this is because the object s no longer in contact with the box so i thought that after a period of time the object would start to decelerate and end up at the back of the box.

Yes, it would.

(pardon the one-line answer)

Originally posted by caspiantiger
ok this ones still kinda confusing me, let me restate it in other terms. Sya there is an enclosed box moving at 30MPH in a northward direction. If an boject that was resting on the floor (not necisarily a heli) would happen to rise from the floor of the box and stay at that hight elative to the floor of the box with no added horizontal velocity would the object eventually move south. The reason i ask this is because the object s no longer in contact with the box so i thought that after a period of time the object would start to decelerate and end up at the back of the box.

your example is a simple question dealing with inertia.

ok in a perfect scenario (meaning the only variables are the one you mentioned) yes the object in the box would stay with same speed. because their will be no other forces acting on the object; which would allow the object to travel freely without interruption.

However i will assume you want a realistic answer(with every variable accounted for). the speed would reduce because there are many other variables that will be present inside the box(but not limted within) along side the object. tho your floating object wont occur in a realistic situation. unless it has a gravitational canceler with it, then the variables from that device will need to be accounted for, at which point this equation moves into the unknown(i havent a clue what effects this device would do to certain physics)


[edit on 28-12-2006 by Glyph_D]

Originally posted by caspiantiger
ok this ones still kinda confusing me, let me restate it in other terms. Sya there is an enclosed box moving at 30MPH in a northward direction. If an boject that was resting on the floor (not necisarily a heli) would happen to rise from the floor of the box and stay at that hight elative to the floor of the box with no added horizontal velocity would the object eventually move south. The reason i ask this is because the object s no longer in contact with the box so i thought that after a period of time the object would start to decelerate and end up at the back of the box.

As Glyph_d replied, it would keep moving north on it's original path until something stops it.

Part of Newton's First Law states "An object that is in motion will not change velocity (accelerate) until a net force acts upon it." (soure: wikipedia) or to paraphrase "an object in motion will tend to stay in motion."

Imagine you're on the space station. Typically, both you and the station are free-falling at 17,000 miles per hour. If you began to hover in a single place, you could theorectically stay in that same position forever. You would not begin to slow down relative to the motion of the station, because there is no net force acting on you. No net force means your velocity will not change. You will not begin to deccelerate and splat up against the back of the space station.

PS: BTW, for all of you who want to critique the validity of my thought experiment, I do realize that the earth's gravity is a force acting on both the person and the space station. But for the sake of this thought experiment, let's just say the force of gravity acts equally upon both.

[edit on 29-12-2006 by Soylent Green Is People]

Yep, another one I didn't read in time.

My girlfriend in her cute ways asked me something similar the other day. She wanted to know if she jumped in the air when a bus slams on it's breaks what would happen.
I had to laugh.
I told her the initial speed of the bus is directly proportional to the physical damage your body would endure.

Basically if the Bus decelerates from say, 60KPH to 0KPH within the time that you are in the air (very unlikely unless it hit something) you will be travelling through the bus at 60KPH, and will inevitably hit the front of the bus at that speed.

But, as I mentioned, the bus wouldnt be able to decellerate that fast unless it hit something... which would be bad for you in any event.

I often like to make fun of star trek. I saw an episode where someone mentioned the enertial dampers were offline, and the captain then gave the order to go to warp 9. lol...
The enertial dampers are what stops you from feeling the effect of the accelleration of the ship.
If they are offline when the ship accellerates to such speeds, you in turn become chunky tomato soup on the back wall of the ship.