at what angle are the raindrops falling relative to the car?
Why does rain appears to be inclined when observed from a moving car?
- Thread starter akc123
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Assume that the pelting is directly.
And so the person in the moving car sees that rain is inclined and a person standing on the road sees the straight rain.
Is my observation correct? When I start saw this I idea it was because of the pressure change caused by moving car or wind.
The angle of inclination increases when the speed of the car increases.
I take fastened a picture:
Answers and Replies
The rain drop has a down velocity of X and a horizontal velocity of 0. Therefore when you are not moving with regard to the raindrop it moves straight down. Now imagine yous are moving with a horizontal velocity of H. Now to you, your Horizontal velocity is 0 (considering you are always still with regard to your own reference frame), so the pelting looks like it has a horizontal velocity of -H to you, and depending on H it volition look like it is slanted.
Pelting observed from a moving car is speed added to what you lot see. It is the same as driving down the road towards a loud horn the speed of the motorcar adds to the frequency of the horn so the pitch audio like a college frequency only when you lot laissez passer the horn and your driving away suddenly the frequency of the horn sounds lower because the speed of the motorcar moving away substracts from the speed of sound.
Rain does not fall exactly straight down air current blows it in a different direction so y'all see rain falling at an angle. Information technology is no different than releasing a helium balloon it never goes exactly straight up the air current blows it abroad as well. Pelting is falling at a pretty fast speed that is why you see angle streaks of rain.Rain observed from a moving car is speed added to what you see. It is the same as driving downwards the road towards a loud horn the speed of the machine adds to the frequency of the horn then the pitch sound like a higher frequency but when you pass the horn and your driving away suddenly the frequency of the horn sounds lower because the speed of the car moving away substracts from the speed of audio.
You're non incorrect, merely I'grand not sure this really applies to the OP'due south question. We can assume that in a near 0 wind state of affairs the rain is falling in a nearly 0 bending direction downward. When the automobile is moving the drops announced to fly in at the angles shown simply because the frame of the moving car makes everything, including the pelting, look like it is moving. Since the rain is also falling, aka moving towards the ground, it appears to come up in at an always increasing angle as the car accelerates.
akc123, your pictures don't show the rest of the rain that doesn't hit the car. Flick yourself continuing on the sidewalk as the machine goes by. You would encounter the rain withal falling straight down. The faster the car goes the more than rain hits it on the forepart. Now imagine yourself in a jet fighter going 1500 mph. The rain appears to exist coming straight at y'all from the front, yet in reality it is falling slowly straight downwardly and you are the one barreling forwards at mach two or so.
At present go back to the situation you described. That component of the raindrop'south motion nevertheless exists, except now it is moving downwardly equally well, and then you at present perceive the increase in speed equally a modify in angle. When the raindrop and the automobile are moving at the same speed, the raindrop appears to come at a 45° angle, equally both the components of its velocity are equal (which ways information technology would be possible for y'all to work out the terminal velocity of rain.)
For a simerlar reason, water goes up a car windscreen when you are going on a moterway in the rain, rather than down. The water is staying still, while y'all are going forrad, and the windscreen is tilted towards you.
You're not incorrect, but I'1000 not certain this really applies to the OP's question. We can presume that in a virtually 0 wind situation the rain is falling in a nearly 0 angle direction downward. When the car is moving the drops appear to fly in at the angles shown simply because the frame of the moving auto makes everything, including the rain, look like it is moving. Since the rain is also falling, aka moving towards the ground, it appears to come up in at an e'er increasing bending as the motorcar accelerates.akc123, your pictures don't show the rest of the rain that doesn't hit the car. Picture yourself standing on the sidewalk as the auto goes by. You would see the pelting still falling straight downwards. The faster the car goes the more than rain hits it on the front end. Now imagine yourself in a jet fighter going 1500 mph. The rain appears to be coming straight at you from the front end, yet in reality information technology is falling slowly direct down and you are the one barreling forwards at mach 2 or so.
Your right, didn't I just say the same matter only in different way. Myth Busters proved this already. One of the experements was to accept 2 people become from a building to their motorcar in the rain. The person that walked got a lot of rain on acme of their head and shoulders. The person that rain got the whole front side of them wet. It turns out the person that runs fast gets wetter. Same thing in the motorcar the faster you go the more rain that will hit y'all. I read some where once that wind resistance simply allows rain drops to autumn at about 35 mph then if you drive a motorcar lxx mph ii times more rain volition hit you. Its basic vector type math you tin prove it on paper. If your moving fast towards the pelting it makes the rain look like it is coming direct at yous because it is.
Your correct, didn't I only say the aforementioned thing merely in different way. Myth Busters proved this already. One of the experements was to have 2 people go from a building to their car in the rain. The person that walked got a lot of rain on peak of their caput and shoulders. The person that rain got the whole front end side of them wet. It turns out the person that runs fast gets wetter.
The thing is, people often care more than about their head and shoulders than the rest of their body. You would probably take to weight the "wetness" depending on which office of the trunk it lands on. Especially as some people wear waterproofs that don't have hoods.
the angle of inclination is given by
tanθ=Velocity of motorcar/Velocity of rain
It is an optical illusion the rain looks vertical because information technology besides looks like its moving torwards you lot when accelerating.Because when traveling at 35mph you lot expect up in to the sky it is a foot away but two sec later it is 1/2 a foot abroad then on your windshield its hard to explain merely pointblank not wind only an optical illusion
Cramerk, I tin't really follow what you lot've said. Is it anything different than what'south already been said prior to your mail?
Hi Torrent Fans....
Well, you are all right to some extent simply no one, I think, is correct to the full extent (nor to be fair, will anyone exist once I take finished this post.....). I preface this all with the fact that I am an anthropologist, non a physicist, nor even a meteorologist, and in the main I but observe things and effort to sort out what is going on. And I accept washed a couple of observations of this miracle which might bear witness interesting, though the truth is I take more than questions than answers to contribute.
Beginning, clearly - every bit all agree - the rain is not moving (sideways) past you at the speed information technology appears, you are moving past the rain at that speed. But the thing about being in a vehicle is it is like Einstein'south train - inside the vehicle you practice not feel you lot are moving because, relative to the vehicle, you are not. Information technology is just the bystander who sees that yous are moving. The pelting is, to some extent, a eyewitness.
Ok. Fine. I am good to that point. The thing that interests me is this. I have noted that if the rain is coming down virtually horizontally - perpendicular to the footing - when I am at rest, then equally I speed up in my vehicle the rain increasingly appears to exist deflected in the angle it is passing my window. At present I get - every bit several have said - that the speed the rain appears to exist moving by my window to the rear is equivalent to the speed I am actually moving forward in my automobile.
Only my interest is non so much the apparent speed of the rain - it is the angle. I have made some adequately careful observations, though certainly non rigorous, and accept institute the following. At most 20 kilometres an 60 minutes (hey, requite me a suspension, I am a Yank but I live in Papua New Republic of guinea, and then it is kilometres - and aye, the r comes before the e at the stop in these parts...) the rain is no longer vertical, but appears to exist coming down at an angle to the vertical of about 30 degrees. When I speed up to 40 kilometres per hr the angle increases to merely most 45 degrees. Then I have doubled my speed for only a 50% or so increase in angle. Just then I take to speed upward to correct effectually 80 kilometres per hr to become the pelting to announced to subtend an angle of sixty degrees – another doubling of speed to attain, this time, nigh a xxx% increment in bending.
These figures may not be - are not - accurate, but I think the blueprint is articulate. If yous plot the speed on the y axis and the credible angle on the x centrality, then the curve is asymptotic. Drakkith was right, the rain appears to be coming at an "ever increasing" angle the faster yous go. Merely two refinements here. First, the angle does not alter at a abiding rate with speed (though what happens with constant acceleration is a question I volition broach below). Second, the implication that if you are going 1500 mph (say 2414.016 kph) in a jet trying to evade the IRS the rain will announced to be coming "straight at you" is, I think, not accurate (and I know Drakkith was just speaking loosely here). The truth is, I am pretty certain, that as the rain goes by the window of the aircraft it will be close to horizontal, but the bending will actually only exist something like 88.5 degrees or 89.15 or 89.62 to the horizontal. It will non be xc degrees.
So that is my question. Or therein resides the nexus of my questions. What is going on here? A couple of specific questions, interlaced with some observations.
Start, Why is it that the curve relating speed to angle is asymptotic? I am certain the answer is simple, but I practise non know it. 2nd, how fast practise you lot have to go in order for the pelting to appear at a true ninety degrees to the horizon? My gut feeling is that the latter answer gets back to Einstein and the speed of light. Indeed, the whole thing feels instinctively like some relation betwixt special and general relativity. The special relativistic aspect is that all motion is relative, and the distinct frames of reference of the stationary bystander (or the rain, were it sentient) and the person in a moving vehicle result in different perceptions. So at that place is the general relativistic aspect which introduces the relation between dispatch and the angle of the rain (not to mention mass, which I just did). Nether a constant dispatch what happens to the angle of the rain in equal time periods? Does acceleration at a certain rate introduce the possibility of change of angle a steady rate, equally opposed to the relationship between speed and angle? In that case increased dispatch would arroyo, but not reach the speed of light in direct relation to the bending of the rain which would approach but non attain the horizontal.
Finally, though the rain appears to alter angle every bit speed changes, the same cannot be said for other features in the environment. For example, houses but appear to pass at a speed equivalent to the actual speed of the vehicle merely they do not appear distorted in the vertical dimension. I have too noted when it is raining hard that strong flows of water coming off the roof of a house appear to laissez passer rapidly, but practice non appear to be distorted in the vertical. I had a lot of trouble seeing the key difference between a spout of water dropping to the ground and raindrops dropping to the ground. But every bit I thought almost this in the past few days it came to me that function of this might be a matter of distance. Could it be that if I drove by a fount of h2o coming off a roof at close range - say ten feet distant - that the angular outcome might be apparent? I accept not been able to do and then without serious hazard to myself and others, so the hypothesis remains untested. Perhaps someone out in that location in a less highly traveled surface area tin conduct the experiment. Information technology also occurred to me it might somehow be a thing of field and ground - does the house somehow establish a ground that prevents the optical illusion from manifesting?
And with respect to the business firm, that led ineluctably to another couple of idea experiments. For instance, what would happen if we had a series of houses falling direct down from the sky at a regular rate ? Would hey would appear - as our speed increased - to be falling at an bending (over again I feel instinctively that this would not happen at distance, merely am less certain about if they were very close to my window). And what the the houses were suspended in the sky, say xv houses, one levitated on top of the other in a line perpendicular to the basis,but immobile (well, relatively...). Would they also appear to describe a slanted line if yous passed them at speed? Does distance affect this?
And a final question - I annotation that when I expect at the individual raindrops as they pass my window at speed it is not a series of horizontal raindrops arranged at an angle in relation to i another, but that, instead, each raindrop, which is really an elongated drop of water perhaps half an inch or more in length, appears at an angle. That is, the private drops are distorted at the same bending as the row of drops. It is the divergence betwixt A and B below (hope this comes out in the text, but I remember yous know what I mean....
A. I B. /
I /
I /
So the question is would those houses appear each to be distorted at an angle to the horizontal besides? And why not??
Sorry for going on, but I detect this interesting and I accept been thinking about this over the by few days because we have had torrential rain with plenty of time for observation. I then googled "why does the rain appear to change angles when you speed upward in a machine" and found this site. It has been a good discovery. Hope I haven't overstayed my welcome, but I would be interested in any reactions....
Thanks
Cadger
Now, the angle. The tangent of the bending of the apparent velocity with the ground is the ratio of V and v: $$ \tan \alpha = \frac Five v, $$ so $$ \alpha = \arctan \frac V v. $$
To merely things somewhat, let's brand the velocity of the rain our unit of measurement of measure; in these units, the formula above becomes $$ \alpha = \arctan \frac 1 v. $$
Fastened is the plot of the bending, in degrees, against the speed of the vehicle (in units of the rain speed).
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