Water Definition and 1000 Threads

  1. K

    Buoyant force and a water column

    Recently I viewed the Searaser video at After watching it, I feel the numbers given in the video could be wrong but not sure. So I'd like to know how I can calculate the amount of water pushed by the Searaser device at some height in one wave shot e.g. at 100 ft, 200 ft and 300 ft above sea...
  2. brotherbobby

    Water flowing out of a tank through a hole

    I assume the water to start flowing from rest at position 1, hence ##v_1 = 0##. Applying the continuity equation, ##A_1 v_1 = A_2 v_2##, we find the (wrong) result that the velocity at position 2 is ##v_2 = 0## also! (We assume that ##A_2## is small but finite) Hence, to answer the question...
  3. brotherbobby

    Weight of water with objects floating

    We understand that the crucial thing about the problem is that the volume of water present in the three containers are not the same. Also, we note that in each case the weight of the container is the total weight of its contents. (A student might be confused as to why should be so - after all...
  4. Harini Krishna

    Calculating the speed of sound in water

    Hi,i want to calculate the speed of sound in water Containing Chlorine : 4mg/L in 1L distill Water Chloroamine : 4mg/L in 1L distill Water Florides : 0.5mg/L + in 1L distill Water Copper : 0.005mg/L + in 1L distill Water Lead : 1.3 mg/L in 1L distill Water Can you please help in...
  5. C

    Schematics of a high pressure water switch

    Does anyone have internal schematics (or illustration) how this thing work inside? Like how water flow can activate the conduction to the two wires connected? https://www.amazon.com/dp/B01MU3KQCD/?tag=pfamazon01-20
  6. T

    Why does water freeze differently when leaves are present on a shelter roof?

    Hello! I wait for the tram in a shelter. The roof of the shelter is made of transparent material (glass like). Leaves fall onto the roof and remain there in early winter during the first freeze. If there are no leaves on the roof (recently cleared by wind), the ice freezes with no...
  7. E

    Deriving the electrostatic pressure of a water droplet

    I assumed a uniform distribution of charge within the droplet such that ##E = \frac{q}{4\pi\epsilon_{0}r^{2}}## at the outside surface. I then said that the pressure acting at the surface would be the force on a charge element ##dq## within an area ##dA## on the surface, divided by the area...
  8. brotherbobby

    Gauge pressure of water oozing out of a pipe

    Assuming water to flow out of the pipe with the same speed as inside and the thickness of water column ##h_{ab} = h_{cd} = h##, my answer would be ##\mathbf{(P_b = P_c) > (P_a = P_d)}##. My reasoning is as follows : at positions ##a\; \text{and}\; d## the gauge pressure is 0 and the total...
  9. V

    Water level in a submerged closed vessel after it is turned upright

    Hello all, I need Your help with one real / theoretical situation. We have submerged pipe filled with air at atmospheric pressure that is closed on both ends. The hole is formed on one pipeline end and the water starts flooding the pipe. Let's assume pipe is tilted somewhat and that no air...
  10. bigyabbie

    Plumbing Compressed air powered water pressure

    Hi there, I have a few interesting problems that I have been exploring for a while now, but i quickly get beyond my level of knowledge of physics, so wondered if members of this Forum may be able to assist. One of the projects that we have been trying to solve is how to maintain a decent quality...
  11. Z

    Still water droplet evaporation rate (help using Maxwell's formula please)

    So I've observed the animal I am studying dry it's self (a survival mechanism called anhydrobiosis) to avoid freezing (laseration by ice crystals). Life forms given time produce a number of protectants in order to survive. Trehalose a sugar is produced to 2-4%. This will act as an antifreeze to...
  12. J

    Why is milk smoother and flatter than water?

    I have conducted an experiment involving projecting a laser beam onto a surface and observing speckles that move relative to us. Those speckles become less visible (maybe smaller?) when the surface is smooth and that is especially the case with milk. I have dyed milk and water to see whether in...
  13. Y

    Entropy change when melting ice then refreezing the water

    ##dmL_f= Q \; \; ##,##∆T=\frac{T(v_l-v_s)∆P}{L} \; \;##,##\frac{dmL_f}{T_0}= dS_2 \; \;##,##\frac{dmL_f}{T_1}= dS_1 ##
  14. V

    Mathematical Modeling of an evaporator for evaporating water

    I am trying to model an evaporator which evaporates water to steam in Matlab/simulink. Are there any governing equations i need to know and follow when modelling the evaporator mathematically? Please let me know.
  15. Zachrz

    Safe Endothermic reactions for skin

    Hi, Its my first time here in PF, I was wondering what could be a fast endothermic reaction(with water) that does not burn the skin/ cause severe allergic reactions when/after touching or in contact with the reaction. (With high rate of cooling and hopefully no bubbles or gas forming). E.g to be...
  16. BWV

    Induction Water Heaters: Are They Worth It?

    Was curious if induction water heaters were a thing and if they had any benefits over a traditional electric resistance coil. On quora someone argues that a resistance coil is a near perfect conversion of electricity to heat, therefore no benefit to induction - is this correct? Is the...
  17. A

    A Visualizing water molecular dynamics in an electromagnetic field

    I am interested in showing a visualization of water molecules in a time-varying electric/magnetic field as part of my PhD work. I would like something like this visualization: , but with an external time-varying field applied. At first, I thought of simply animating water molecules...
  18. S

    Heat loss from a hot water tank

    This is a past exam paper Q. I think i might be missing info though. For i) i use q=UAdT A= 35m2 dT= (80-20) They haven't given U but if i know answer should be 1,050W So if i set U to 0.5 (0.5)(35)(60) = 1050W Am i missing something or could I calculate U with the info given? Also ii) Use...
  19. Amik

    Conservation of momentum — Water dropped from a firefighting airplane

    I could not unserstand part d.Does problem ask about plane's speed immediately after it starts to drop water or after the water is dropped completely?
  20. L

    Superionic and metallic states of water and the Anomaly of Water

    https://www.wired.com/story/a-bizarre-form-of-water-may-exist-all-over-the-universe/ Black iceI knew the Black Ice Theories since around 1990 https://www.nature.com/articles/s41586-019-1114-6 -- Demontis, P., LeSar, R. & Klein, M. L. New high-pressure phases of ice. Phys. Rev. Lett. 60...
  21. vxiaoyu18

    Asking for help with a physical problem that uses a piston to push water

    Consult a physical problem that USES piston to absorb water: Pistons with surface areas S1, S2 and S are placed horizontally at the same height (H). S1 = S2 S=S1+S2 When F starts moving to the left, how do you calculate its force? Is F=ρgHS? (*The friction force doesn't have to be calculated.)
  22. R

    Personal Jet Boat Water Craft Thrust Question

    Assume a jet boat or personal water craft (JetSki, etc) has a movable propulsion nozzle. This nozzle can be moved vertically so that the water jet driving the boat forward can be either above the surface or below the surface of the water. Further clarification. You are speeding along on your...
  23. E

    Internal energy of a container filled with water & steam

    I've worked out that half of the steam must condense (since the pressure of the steam needs to remain constant for the forces on the massless piston to balance). Also, if the total volume of the container is ##V##, the work done on the system equals ##\frac{P_{atm}V}{4}##. When half of the steam...
  24. T

    Impact of Atmospheric Pressure on the Water in a Tank and a Pipe

    Hello all I was hoping someone could help with understanding how fluids level out under atmospheric pressure. For example:- Below is a picture of a tank of water with a closed door at the bottom, the door leads to an inclined pipe that is closed off at the end there is another pipe connected...
  25. M

    Bernoulli's Equation and water rockets

    So I'm playing around with some water rockets and I'm trying to figure out how fast the exhaust velocity of the water is. I've had an experimental approach using high fps camera to record and analyse (using tracker) the exhaust velocity. I'm using a 0,5 l soda bottle with 0,085 L ; 0,135 ; L...
  26. C

    Perfect Espresso Water Chemistry

    Hey all, I've come here to seek out some help creating the perfect espresso brewing water. I've done some research, and I think I've reduced it down to a chemistry problem. I'll be starting with distilled water and adding minerals, some 'hardness' and an 'alkalinity buffer.'First, here's the...
  27. D

    Calculate the amount of water vapor

    Hello 4m3/min is 240m3 /hr. Temperature is 293K, at 25C the amount of water is 22.8g/m3 and at 20C it is 17.1g/m3. Relative humidity is 70% and absolute pressure 9bar. Solution: @ 25C relative humidity lowers the water content from 22.8 to 15,96g/m3 so in total 3830.4g/hr 240m3 or air is...
  28. T

    Engineering Calculating the Moments on the Walls of a Tank filled with Water

    Hello all, I was hoping someone could help me calculate the moment a tank wall experiences. I have the following question:- Tank contains water with dimensions: 4m Wide 12m Long 3m Tall Determine the moment at the bottom of the long side at its centre. I have drawn a sketch of the tank and...
  29. Elder1994

    Find the electric dipole moment for a water molecule

    The equation that we saw in class is for a continuous charge distribution, I think that for this exercise I need to treat the system as a discrete charge distribution but I'm not sure. Also, I don't know how I can calculate the intensity of the electric field needed to move this charge.
  30. S

    Water temperature with two materials cooling it

    I converted dm3 to m3, all the degrees to kelvins and found out the specific heat constants of iron and aluminium (0,45 and 0,91 KJ/kg K), but now i am failing to understand how this was supposed to be calculated. The equation given doesn't really help, as there are two unknowns in it: Q and the...
  31. kendreaditya

    Time to Equilibrate 0C Copper & 75C Water

    I have a copper cylinder that is at 0C, how much time will be needed for it to equilibrate with 10kg of water at 75C? Copper cylinder: Mass: 105.7 g Specific heat: 0.385 J/gC Initial Temp: 0C Final Temp: 75C ish SA: 25 cm^2 Water: Mass: 10000g Specific heat: 4.184 J/gC Initial Temp: 75C...
  32. S

    Plumbing Order of devices in the main water line?

    I have a house where water enters from the street in a 1" PEX line, which comes up from the slab inside a closet. No other permanent plumbing is yet installed. I want to install a shut-off valve, a pressure regulator, pressure valve, and a sediment filter. I'm also considering installing a...
  33. J

    System to collect a small amount of water from the air

    Is there a well-known system that can collect small quantities of water from air, like maybe 6 oz/day? Should take up at most a cubic foot
  34. Benjamin_harsh

    How Far is the Boat From its Original Position?

    A boat goes upstream for 3 hr 30 min and then goes downstream for 2 hr 30 min. If the speed of the current and the speed of the boat in still water are 10/3 kmph and 15/2 kmph respectively, how far from its original position is the boat now? With reference to ground, the water travels...
  35. A

    Carbon atom larger than a water molecule? Measuring a molecule's size?

    So there's a website here: https://learn.genetics.utah.edu/content/cells/scale/ That shows the scale of various entities (coffee bean, viruses, a carbon atom, a water molecule etc). It says that the carbon atom is larger than the water molecule. This is based on the 'van der waal radius'...
  36. Tryhard314

    Salt water and potential difference

    Imagine a container of salt water at 0V (Relative to ground),Now you've put in it 2 electrodes,one at +500V (Electrode A), The other at +250V(Electrode b), Normally positive ions should go to the negative electrode , and Negative ions should go to the positive electrode , But in our example the...
  37. F

    B Sailboats providing their own wind

    I happened to be watching this cartoon and this one scene seriously bothered me... This... just feels like it wouldn't be a workable solution. Am I wrong? I can't say I perfectly understand how fans or propellers work, but I would imagine that by pushing air or water in one direction, equal...
  38. M

    Does water flowing through a pipe make noise?

    I've my small incursion team entering a 10 foot diameter water outlet pipe using electric sleds for propulsion and was wondering about sensors in the pipe detecting them. They're wearing suits that mask their IR, but what about noise? The pipe flow is 3.18086e+07 l/h with a 1.25 m/s current...
  39. bubble-flow

    Oscillation of a particle inside water caused by a sound wave

    I don't really know where to start as this is not exactly my homework and I finished school some 15 years ago. I looked into my old high school notes, the last time I ever had anything about mechanical waves and sound. Unfortunately, we never learned anything about sound waves causing...
  40. K

    What is the use of sodium bicarbonate and electrolyzed water?

    I've bought a cleaning agent which advertises that it contains "sodium bicarbonate and electrolyzed water"and is "different" from normal cleaning detergent. In fact, what is the home use of such chemicals??
  41. WhiteWolf98

    Clausius-Clapeyron equation to estimate sublimation pressure of water

    Before this question, the questions were about the Clapeyron equation, and how to estimate ##\Delta s##. I'm completely put off by this question however, and don't know where to start. I've found that the triple point of water is at ##0.01°C##, and there is indeed data in the table for...
  42. T

    How To Calculate The Force Of Water Exerted On A Full Tank

    Hello Community I was hoping someone could me with the following question:- A rectangular tank contains water. It is 12m long, 4m wide and has a height of 3m. If the tank is full determine:- 1) The Force on the long side 2) The Force on the short side 3) The moment at the bottom of the long...
  43. Y

    Differentials of Entropy for Air and Water at Different Temperatures

    for a)##\Delta S=\mp \int_{T_i}^{T_0}\frac{C(T)}{T}dT## and ##\Delta S_{th}=\int_{T_i}^{T_0}\frac{dQ}{T_0}dT## so ##S_{univ}=\Delta S_{th}+\Delta S##. What is ##dQ## equal to ? I don't know how to answer question b). Thank you for your help.
  44. F

    Water Pressure at the tap and practical Bernoulli equation

    Hello, I think I understand how Bernoulli equations works but I am clearly uncertain on some aspects of its application. For example, let's look at the figure below: 1) The static pressure is ##60## ##psi## from the city water supply. There is not flow (tap closed) so the pressure at the...
  45. EEristavi

    How Do You Calculate Torque Generated by Water Flow?

    I know that I have to calculate force that is generated by water. However, I do it wrong way. ## A = \pi r^2 ## ## v = \frac Q A = \frac Q {\pi r^2}## ## F = P t = mvt = ...? ## - have problem with mass. and is it even correct way? if I can calculate F - its easy afterwards... ##\tau = F l ##...
  46. EEristavi

    Water Pressure and 2 dimensional motion

    $$ H = \frac { V^2 - V_0^2 sin \Theta} {-2g} $$ $$ H = \frac {V_0^2 sin \Theta} {2g} $$ So, I need to calculate ## V_0 ## I'm thinking about pressure. $$ P = \rho g \Delta h $$ $$ \Delta h = h - L sin \Theta $$ $$ F_A = P S_A $$ $$ F_A = P S_B $$ Dead End here...
  47. saxman2u

    How to calculate TDH of PVC downspouts and water tank height?

    Greetings, Looking for the best way to calculate TDH for some rainwater catchment systems I am designing in Texas. Some homes we are installing these systems on have large footprints, between 6,000 to 8,000 sq feet. The large rainwater collection tanks we install range between 30,000 and...
  48. kunalvanjare

    How can I achieve homogeneous in-line mixing of a Coolant with water?

    Hello guys, This is for a new product I am designing, which involves topping-up or refilling the liquid into a CNC Machine or Part Washer. I have to mix about a Litre of the chemical (alkaline.. pH in the range of 8-12) with about 50 Litres of water. The water will be fed under gravity through...
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