You're Driving 30 MPH ~~~~~~~~~

[Trakanonn]

You're driving 30 MPH down the road, window open.

Outside the window is a bird, flying parallel 30 MPH.

Then Bird decides to fly inside the vehicle while keeping its speed.

What happens?


Does it fly into your windshield? or does it just chill in midair since you're going 30mph too?

[Blueobelisk]

I'm the smartest man at math and physics in these forums.

If you're both going 30 miles per hour then your reference frame will be the same and you'll be travelling together of course. It'll look like it's in midair, even if it's not inside your car.

I don't feel like drawing the graphs that will make you understand better. Unless you decelerate then the bird will keep up. If you accelerate then it hits the back windshield.

[Spectral]

I'm pretty sure that the limiting factor on speed for a bird is mostly air resistance. Diving in behind the windshield cuts the wind resistance to nothing, and it immediately flies forward and hits that windshield hard as hell.

[Firebert]

As soon as the bird enters the vehicle it stops having to fly at 30mph against the air and is instead in a closed environment in the car.

If it continues to fly at 30mph, it hits the inside of the windshield. Otherwise, it can stop flying and land on your steering wheel or something.

[obdigore]

The speed at which the bird moves forward 'inside' your car depends entirely on where it is in your vehicle in relation to the window, and the size of the window.

Assuming, of course, you are implying the bird continues to exert the same force to move forward as it was while it was outside your car.

[Dendrek]

That bird would experience a big hit in wind resistance before it got into your car. Assuming it was "casually" flying in a forward direction, as soon as it drifts too close to your car, the increased pressure of the air flying past your car is going to throw off its trajectory and lose its calm, forward motion. If it manages to get inside of your car, it will no longer be sailing forward as it was, and will instead be a quaking, pecking, flapping nightmare that will probably slam into you or stumble into your back seat. Either way, I think the last thing it would do is continue smoothly flying forward (to slam into your windshield) or appear stationary (flying gracefully next to you).

[Deleted]

I'm the smartest man at math and physics in these forums.

If you're both going 30 miles per hour then your reference frame will be the same and you'll be travelling together of course. It'll look like it's in midair, even if it's not inside your car.

I don't feel like drawing the graphs that will make you understand better. Unless you decelerate then the bird will keep up. If you accelerate then it hits the back windshield.

Hilarious reply, given you provided no math whatsoever.

As soon as the bird is inside there is little to no air resistance except for the air floating inside the car through the window which is rather insignificant (fuel wise this is costing you an extra 5-10% extra fuel).

The clue lies, surprisingly, in the biology and the psyche and instinct of an animal: the bird will not keep the same pace since it will panic due to the sudden, unforseen change of airflow, and this panic will likely somehow cause the bird to crash somewhere. One theory how it'd crash is into a window, especially if its a clean window, as it tries to fly away. Another one is related to physics indeed (but you did not address at all) the bird is slightly flying upwards while its outside because of the wind going downwards under it. This airflow is gone in the car. That makes it likely the bird will crash into the top of the car.

[Dendrek]

P.S. It would be funny as hell to watch (from an adjacent car) until the car accident that immediately follows.

[Adam Jensen]

As soon as the bird enters the vehicle it stops having to fly at 30mph against the air and is instead in a closed environment in the car.

If it continues to fly at 30mph, it hits the inside of the windshield. Otherwise, it can stop flying and land on your steering wheel or something.

Eh, depends on frame of reference.

If it gets inside your car and flies at 30 mph in relation to the Earth, then it will appear like its floating in midair in relation to the car. It's speed in relation to the car would be zero.

If it goes into the car and speeds up to 30 mph in relation to the car, it is now doing 60 mph in relation to the earth, and it will crash through your windshield.

Note, I'm not taking air resistance into account here.

[Very Tired]

The bird and the car combine speeds, for a total of both traveling at 60 mph, right?



But what if a car is traveling 30 mph on a spaceship going at the speed of light, is the car essentially moving faster than the speed of light?

[Endus]

It's not really "air resistance", it's wind speed. The air outside is mostly static. The air in your car is mostly traveling at 30mph. So it's like the bird hits a gust of wind behind it, and that's why it hits the windshield; because its speed is relative to the air it's flying in, not the ground beneath it.

This is also why you can go to the beach on a windy day and see seagulls trying to fight against the wind and getting nowhere, or even moving backwards; their air speed isn't outpacing the wind speed.

[Dendrek]

The bird and the car combine speeds, for a total of both traveling at 60 mph, right?

That's clearly not how speeds combine. It's multiplication, my uneducated friend. They'd be going 900 mph...

[poser765]

That bird would experience a big hit in wind resistance before it got into your car. Assuming it was "casually" flying in a forward direction, as soon as it drifts too close to your car, the increased pressure of the air flying past your car is going to throw off its trajectory and lose its calm, forward motion. If it manages to get inside of your car, it will no longer be sailing forward as it was, and will instead be a quaking, pecking, flapping nightmare that will probably slam into you or stumble into your back seat. Either way, I think the last thing it would do is continue smoothly flying forward (to slam into your windshield) or appear stationary (flying gracefully next to you).

Truth to this.

Now let's look at how things fly and discount all the above rapid change in airflow.

In order for a "thing" to generate lift it needs to have an airfoil traveling through the air at a certain velocity (well or at a certain angle, but lets KISS). When the bird is outside the car the airflow over his wings is enough to keep him flying...probably a LOT more than is enough. Inside the car that airflow doesn't exist. As spectral also pointed out there is a fair amount of air resistance (drag) effecting the bird which means he is probably working pretty hard to go 30mpg. He is exerting a lot of energy.

When he enters the car he loses that AIR velocity, and thus loses lift. He starts to fall ever so very briefly. Now he ALSO losses drag, but doesn't change how much he is working...lets call that thrust. Since all that drag is gone, and thrust is the same the bird begins accelerating through the air INSIDE the car...will call that relative wind. AIRSPEED increases, lift increases and the bird continues to fly. Again since the drag is gone and thrust remains the same, he plows into the windshield.

[eschatological]

The bird never even makes it in your car.

Assuming the bird stays at 30 mph, it'll probably crash into your rear seat window, as it'll have to come in at an angle, and, while its speed will still be 30 mph, its momentum in the forward direction will be less than 30 mph.

IOW, the bird has to travel the hypotenuse of the triangle formed between your window, itself, and your window in however many seconds, and the hypotenuse is a^2 + b^2 = c^2, IE, longer than B, which is the distance of your window to your window at some undetermined time in the future. And since you're both travelling 30 mph, it'll take longer for the bird to travel the hypotenuse, than it takes you to travel the straight side.

/math

[obdigore]

That's clearly not how speeds combine. It's multiplication, my uneducated friend. They'd be going 900 mph...

No no no, 900 has zeroes in it, and when you multiply with zeroes the result is always zero. So they both would instantly stop.

Perhaps we should institute a more effected emergency brake? Introduce bird to car.

[Dendrek]

It's not really "air resistance", it's wind speed. The air outside is mostly static. The air in your car is mostly traveling at 30mph. So it's like the bird hits a gust of wind behind it, and that's why it hits the windshield; because its speed is relative to the air it's flying in, not the ground beneath it.

This is also why you can go to the beach on a windy day and see seagulls trying to fight against the wind and getting nowhere, or even moving backwards; their air speed isn't outpacing the wind speed.

The air in the car isn't static (especially if the window is down). It's going all over the place, which would play hell on any attempt of the bird to maintain lift. It would probably be like the bird getting caught in a small tornado. So rather than flying forward really fast, I think the bird's direction and elevation would get thrown off quickly, resulting in chaos rather than a front windshield slam.

[poser765]

It's not really "air resistance", it's wind speed. The air outside is mostly static. The air in your car is mostly traveling at 30mph. So it's like the bird hits a gust of wind behind it, and that's why it hits the windshield; because its speed is relative to the air it's flying in, not the ground beneath it.

This is also why you can go to the beach on a windy day and see seagulls trying to fight against the wind and getting nowhere, or even moving backwards; their air speed isn't outpacing the wind speed.

It's both...air speed AND resistance.

- - - Updated - - -

The air in the car isn't static (especially if the window is down). It's going all over the place, which would play hell on any attempt of the bird to maintain lift. It would probably be like the bird getting caught in a small tornado. So rather than flying forward really fast, I think the bird's direction and elevation would get thrown off quickly, resulting in chaos rather than a front windshield slam.

True, it's not static, but it's really not ALL that turbulant, and the air is largely moving towards the window.

[Delekii]

The implication of the OP is that the bird maintains the force necessary to maintain 30mph.

Then Bird decides to fly inside the vehicle while keeping its speed.

Ergo; it floats in midair in relation to the vehicle. Is it realistically likely or possible? Doubt it. But as the scenario stands in the OP, yes.

[Dendrek]

True, it's not static, but it's really not ALL that turbulant, and the air is largely moving towards the window.

But it's turbulent enough that maintaining equal lift (or lift at all, really) in both wings would be nearly impossible. It's like an angled gust of wind suddenly hitting a bird (only much worse because not all the air in the car has the same directionality). A bird won't continue to fly straight in such conditions.

[Adam Jensen]

The bird and the car combine speeds, for a total of both traveling at 60 mph, right?



But what if a car is traveling 30 mph on a spaceship going at the speed of light, is the car essentially moving faster than the speed of light?

Problem is, on a spaceship going C, the car would not be able to move, in relation to the spaceship, because that would require greater than infinite energy.

In fact, a spaceship can't even go C, because that requires infinite energy, but that's besides the point.

Mathematically, yes, a car would be doing C + 30mph in your scenario, but it can't physically happen.