one day you were standing on the shore of a small lake. you looked out onto the water and saw a boat. in the boat were two men with five huge steel beams. the men were sidling the beams out of the boat and into the lake. if you could actually see it or measure it, would the level of the water in the lake be rising, falling, or staying the same?
2227
This comes from a brain teaser but I'm not sure I can solve it:     You are in a rowing boat on a lake. A large heavy rock is also in the boat. You heave the rock overboard. It sinks to the bottom of the lake. What happens to the water level in the lake? Does it rise, fall or stay the same?   I'd say that the water level drops, because when you drop the stone in the lake, the water level rises according to the volume of the stone, BUT the water level decreases by a volume of water weighting the stone's weight, when you take it off the boat.  Is that correct?
70584
In  someone mentioned that it couldn't happen. Why not?   For example I asked about the speed an object would have to move at sea level to create a vacuum behind it; in the comments someone asked what I meant by vacuum because there couldn't be a perfect vacuum.
13956
I'm studying for my upcoming physics course and ran across this concept - I'd love an explanation.
62459
There is an experiment we learned from high school that demonstrated how atmosphere pressure worked.  Fill a cup of water and put a cardboard on top of it, then turn it upside-down, the water will not fall out. The explanation said this was because the atmosphere pressure was greater than the water pressure, which holds the water up.  I believed this explanation once, until I found some points that confused me:  1. Is the water pressure in the cup really smaller than the atmosphere pressure?  This is what we have been taught through our life. However, consider an object in the water under sea level, it experiences the pressure from water plus atmosphere pressure. So the water under sea level must be greater than the atmosphere pressure. Even it is contained in a cup, the pressure wouldn't change. Is this True?  I read . If the cup is fully filled, the compressibility of water is much greater than that of the air, also the surface tension of the water keeps the air out of the cup. So the water is held in the cup. This explains the problem. But I still want to ask if the water pressure smaller or greater than the atmosphere pressure in this situation.  2. When the cup is half filled with water, why it still holds?  I saw most of articles or opinions against this. They all agree that the water would not fall only if the cup is entirely filled. But I did the experiment myself, the water stayed still in the cup even it is not fully filled. Actually even with little amount of water, as long as it covers the open of the cup and the cardboard on it, the water stays in the cup.  Even the compressibility of water is much smaller, the air inside the cup provide enough compressibility, how come it still holds?
28373
My framing in the following photo completely failed to capture the sheer height of the waterfall.  If you don't know I was standing at the top of the waterfall, and the "splinters" at the bottom are full-size tree trunks 2 feet in diameter, you wouldn't have a clue how tall it is.  It just looks like a smaller, shorter waterfall shot with a slower shutter speed.    My question isn't about this picture or waterfalls in particular, but about framing to capture the scale of your subject in general.  What are techniques to show just how big something really is?  Or conversely, something really small?  Especially things like rocks or water that look roughly the same at any size.
50431
Why the log? Is it there to make the growth of the function slower?  As this is a common experimental observable, it doesn't seem reasonable to take the range from $[0,\infty)$ to $(-\infty,\infty)$ (For a particle emitted along the beam axis after collision $\theta = 0$ wouldn't be better to have a number that says how close it is to zero rather than one that says how large a number it is. I hope that makes the question clear.)
59244
I saw  by  and I was not 100% sure about the third phenomena, a statically charged object attracting a stream of water, especially because he explicitly mentioned that it is not due to the  of the water. A week later he uploaded an  all five phenomena and he says it is because of repelled equally charged ions, back up the water flow, such that the water actually falling along the charged object would be oppositely charged and therefore attracted. Here is a still image from the video illustrating this:    However this explanation seems strange to me, since this would mean that this way you could build up a charge in the water which has exited the tap (as well as in the water inside the tap as well). Therefore it should get harder to push those ions back over time, and therefore there also would be a decrease in the attraction of the water (assuming there is no other way to discharge it). I have tried a simple similar experiment, where I catched the water leaving the tap in an insulated bowl, but I did not notice a decrease in attraction.  There a couple of reasons why my experiment does not rule out his theory:   I was holding the charged (plastic) object by hand, which caused that its distance to the water stream varied, making it difficult to observe a decrease in attraction. I only conducted my experiment for roughly 30 seconds, which might be enough time for a opposite charge to build up.   The reason that he mentioned why permittivity can't cause this phenomena is because the electric field would be homogeneous and therefore the attractive and repulsive force of both dipoles of a water molecule would cancel out. However the electric field would only be homogeneous if the charged object would be an infinitely large plate, which it isn't. Thus water molecules would be attracted to the charged object. In order to make the permittivity theory more plausible I thought of maybe doing a order of magnitude calculation to see if it could generate a large enough force would be able the water stream by the observed amount. However I do not know what a good guess would be for variables such as the amount charge on the charged object and how the electric field would fall off over distance.   So, my question is whether his theory is really correct, or if the permittivity of the water can cause it.
121321
When it's raining, would you get less wet if you run or more wet?  I think you will get less wet, because rain is coming down in a constant volume and if you run you will have a shorter amount of time you will get less volume  I'm not too sure though, some people say when you run you are running into a more volume of rain because rain is not all coming up to down, it will hit you more horizontally
16088
Our class is learning about hydrostatic water pressure and we have been told that we can calculate the force of the liquid on an object at any depth using "the density x 9.8 x the depth". However, as the depth increases, wouldn't the density of the liquid increase because of the weight of the liquid above it compressing it? So should't there be something in the equation to account for the varying density? To me, "density x 9.8 x depth" seems like it is saying that the density will be constant...
73754
I would like to know the following:   What is the angle at which water gets splashed when I ride my vehicle through a water on the road? How does angle of water varies with speed? What is the relation between the distance the water goes with the speed of the vehicle?   Thanks!
1998
I'm calculating the force of a body hitting water from a high height. So far I've figured out the velocity at the time of collisions would be 40 m/s. The body is 78 kg. I seem to need the time it takes for it to accelerate to a stop after hitting the water but I can't find any concrete numbers for that, what would be a good estimation?
124138
Yesterday my friends and I were solving this easy-looking question:  A metal cube is placed in an empty vessel. When water is filled in the vessel  so that the cube is completely immersed in the water, the force on the bottom of the vessel in contact with the cube: (A) Will Increase (B) Will Decrease (C) Will remain the same (D) Will become zero  At first we thought the answer to be (B) considering the buoyant force acting opposite to the weight of the cube. But then, a question popped up in my mind: &quot;What causes this buoyant force even if no fluid was actually displaced?&quot; So I referred to the Archimedes' Statement:  Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. — Archimedes of Syracuse  But according to the question, no such fluid was displaced by the block ! So, here are my questions:  What is the basic reason behind buoyancy? Is it the pressure difference in fluids or the 'liquid-displaced' theory?  What must be the answer to the question (That I was solving) ?  Considering the case that you may say- &quot;The reason behind buoyancy is the pressure difference in the fluids&quot;; Will there be no buoyant force applied to the iron cube as there is no fluid layer present below the cube i.e. no pressure difference?   (Considering the iron cube is VERY dense and thus not allowing any fluid layer to push its way below it)  Or you might add another statement to the above question that-&quot;Yes, buoyant force is applied as there is always a fluid layer present below it...&quot; .Please do explain yourself.  If your answer is according to the Principle given by Archimedes of Syracuse , will there be no buoyant force on the cube as the cube didn't actually displace any fluid? Just like the case where you may consider it to be a part of the vessel itself.
5314
The sun is shining and a spherical snowball of volume 340 ft$^3$ is melting at a rate of $10$ cubic feet per hour. As it melts, it remains spherical. At what rate is the radius changing after $2.5$ hours?   And this answer is wrong? please help $10\times 2.5 =25$ $340 - 25 = 315$ so $r^3 = \dfrac{315\times 3 }{ 4\pi}$ $r= 4.2$ ft
5991
As I learned today in school, my teacher told me that when light enters a glass slab it slows down due to the change in density and it speeds up as it goes out of the glass slab. This causes a lateral shift and the light emerges out from the point different than that from where it should have actually emerged from.  Okay so what I mean to ask is, when light enters point A on glass slab and emerges from point C why does the light speed up? Where does it get the energy it has lost when it entered the glass slab?  P.S.: Also, if I place a very very very large glass slab and make a beam of light pass through it will the light never come out as all the energy was lost in place of heat?
67451
If I understand the first bullet correctly        You instantaneously move or otherwise change the flow of the water as you direct, up to 5 feet in any direction. This movement doesn’t have enough force to cause damage.      One could freeze the water in a 5 ft cube, step onto it, and then raise the cube into the air, though only 5 feet per round. Since the cantrip doesn't mention any carry limit.   Is this possible, or does the first bullet not apply once the water has been frozen?
115703
Today accidently I poured a little bit of water on a very hot pan , and something weird happened , where the quantity of water split into smaller spheres that moved around fast in the pan. I'm wondering about the physics concept behind that..
63945
Imagine that a mast of a sailboat is $186,000$ miles long, and the sailboat is moving to the right at a constant $10$ miles per second. If you drop a ball from the top of the mast, the ball will land exactly at the base of the mast. The ball has two components to its velocity. If the experiment is repeated with a pulse of light instead of a ball, then the pulse of light only has one component of velocity. The pulse of light is going directly down at $186,000$ miles per second, but the pulse of light is not going to the right at $10$ miles per second since the speed of light is independent of the speed of the source of light. Therefore, I would assume the pulse of light would miss the base of the mast by $10$ miles. Would the pulse of light actually hit the base of the mast?