when they paint the waterline on a boat, how do they determine the waterline without floating it?
476567
Well, I have no idea what a waterline is on a boat, but that's to be expected with me, isn't it  :-)   Figure on this.......somebody way way way back, when they very first decided to paint waterlines on boats, may have had the smarts to float boats of various sizes and weights and/or float models scaled to size/weight, and take notes.  So, supposing someone did that once upon a time, some other smartass made some permatable for it, and it became common practice  :-)\nIt's all a matter of physics, I'm sure.\nAre you home yet?
291004
if an object is floating, the buoyant force on it equals its weight -- the vertical forces have to sum to zero.  try drawing a free body diagram to convince yourself of this.
549460
bmck has it right...prep work on any paint job is about 3x the actual paint time and the more the better...all loose paint must go; any place the aluminum is oxidizing ( loose grey powder, the alum. equivalent of rust) must go. Zinc chromate either in spray cans or quarts is the preferred  general purpose primer..\n\nPaints are usually made as a system, ie a finish coat is made to go with a specific primer. GO to marine store..or, if you are on fresh water and doing very limited use) a hardware store, and read the pant cans. Having spent 30 years reading Interlux and Pettit cans, I know there's a lot of information on the label.\n\nIf you are thinking of putting an anti-fouling paint on the boat you CAN NOT NOT NOT use copper based paints. The copper in salt water will eat the aluminum hull in no time....special paints are made for aluminum; once again read the cans.....THIS ALSO APPLIES TO OUTDRIVES AND OUTBOARD MOTORS, FOLKS..if you're in salt or even brackish water don't use copper anti fouling paint on your engine parts.you will quickly regret it
1020782
Principle of all boats is that of buoyancy. Objects will float (will have buoyancy) when the volume of the liquid that they displace is equal in mass to the mass of the object. In a way, you can imagine a 1-to-1 tradeoff. When you place a boat of X volume in water, it displaces (pushes aside) X volume of water. That X volume of water, if you can take it out and weigh it, will equal the weight of your boat. So you can do some calculations for "displacement" (the volume that your boat takes up in water) and then calculate the mass of the water it displaces. If the mass of the water you displace is greater than the mass of your ship, it will float.\n\nNo matter what, make sure the boat is waterproof. In olden days wooden boats were sealed with tar and wax. Any waterproof substance (usually an oil-based resin) should help seal the boat.\n\nYour boat moves faster if it displaces less water. But wait..there's clearly another trade-off here: if you have a lot of displacement, you float better, but that also means your boat takes upa lot of volume, and that will increase water resistance and make your boat slower. So your task here is to find a volume of displacement that allows your boat to float while it doesn't take up so much volume that it will slow the boat down. One solution is to make the hull (underside that is beneath water) more hydrodynamic (more flowy). You can experiment with  different designs (if the materials permit) such as a standard hull or a catamaran. The principles of hyrdodynamics are similar to aerodynamics: sharper contours are less resistant than square shapes. Think of an arrow going through air versus a square brick.
1084334
The water bath is used to cool the solution to the needed temperature.  You set the beaker or flask in the bath.  Which is basically a pan of water.  The weighing boat is used to keep from putting the chemical directly on the balance. You will need to take the mass of the boat and then subtract this from the mass of the boat and the chemical to get the mass of the chemical.  The wire loop is usually platinum or nickel-chromium it is used to introduce chemicals into flame so that  the color produced can be observed.
318231
Let B equal the weight of the boat, say in pounds.  Then B pounds of water will be displaced.\n\nSince there are 62.43 pounds of water in a cubic foot, then a boat of weight B pounds will displace B/62.43 cubic feet of water.\n\nIn your case, with a boat weighing 750 pounds, the boat will displace 12.01 cubic feet of water.  To determine how deep the boat is in water you need to know the geometry of the boat.
920556
WOW Joyce, your question is the second time I've ever heard of (actually SAW it the first time) something like this.\nWe'd discovered that the water stabilizer had reacted with one of the pigments in the paint inside making both, a gas pocket, AND a cloudy mixture inside. Unfortunately, there's not a whole lot you can do about it except for taking it back where you bought it from and maybe trading it for another?\nHope that helps.
563919
Assuming that the cardboard is water tight:\n\nBuoyancy force = Weight of water displaced\n\n(mass of boat)*g = (desity of water) * 4ft*5ft * height * g\n\n81820g = 1g/cm^3 * 18581 cm^2 * height\n\nheight = 4.4 cm, which is the waterline when the boat weighs 180 pounds.\n\nYeah, it sounds quite unbelievable, but most boats that large with a height of 1 foot can hold over 1100 pounds of weight before completely sinking.
1008323
Submarines use a air ballist system, usually running the length of the watercraft along both sides. When the submarine requires depth (diving) these empty tubes (ballists) are filled with sea water, raising the density of the submarine and causing it to sink. When surfacing is required, the water is pumped out of these ballists and filled with air, lowering density and causing the submarine to rise in the water. To maintain a depth goes along the same principles; a necessary mixture of water-to-air is held within the ballists and maintains the submarine's current depth.\n\nT.
1168031
It is done with a paint spraying machine and a line marker.\nIt rolls on 4 wheels and a nozzle is pointed down and the color comes out.
576542
The outside of the paint can will give you directions and will also inform you as to the amount of space that a gallon of paint(for example) will cover....HOWEVER.. be careful.. there is a difference if you use a roller or a paint brush.
496939
in the middle of the sea on  a small boat.... I dont know.  On a ship or at a lot of resorts there is one common way... Reverse Osmosis.  Plain and simple, it's pushing the water through a series of filtrations... multimedia and then through membranes at high pressures.  It is then treated with a variety of chemicals.\n\nThe old way to do it on ships is through multi-staged flash-type distilling plants where the water is boiled at 68F-72F under a vacuum and then treated with a Brominator.
120158
The standard definition of floating was first recorded by Archimedes and goes something like this: An object in a fluid experiences an upward force equal to the weight of the fluid displaced by the object. So if a boat weighs 1,000 pounds (or kilograms), it will sink into the water until it has displaced 1,000 pounds (or kilograms) of water. Provided that the boat displaces 1,000 pounds of water before the whole thing is submerged, the boat floats.\n\nIt is not very hard to shape a boat in such a way that the weight of the boat has been displaced before the boat is completely underwater. The reason it is so easy is that a good portion of the interior of any boat is air (unlike a cube of steel, which is solid steel throughout). The average density of a boat -- the combination of the steel and the air -- is very light compared to the average density of water. So very little of the boat actually has to submerge into the water before it has displaced the weight of the boat.\n\nThe next question to ask involves floating itself. How do the water molecules know when 1,000 pounds of them have gotten out of the way? It turns out that the actual act of floating has to do with pressure rather than weight. If you take a column of water 1 inch square and 1 foot tall, it weighs about 0.44 pounds depending on the temperature of the water (if you take a column of water 1 cm square by 1 meter tall, it weights about 100 grams). That means that a 1-foot-high column of water exerts 0.44 pounds per square inch (psi). Similarly, a 1-meter-high column of water exerts 9,800 pascals (Pa).\n\nIf you were to submerge a box with a pressure gauge attached (as shown in this picture) into water, then the pressure gauge would measure the pressure of the water at the submerged depth:\n\n\nIf you were to submerge the box 1 foot into the water, the gauge would read 0.44 psi (if you submerged it 1 meter, it would read 9,800 Pa). What this means is that the bottom of the box has an upward force being applied to it by that pressure. So if the box is 1 foot square and it is submerged 1 foot, the bottom of the box is being pushed up by a water pressure of (12 inches * 12 inches * 0.44 psi) 62 pounds (if the box is 1 meter square and submerged 1 meter deep, the upward force is 9,800 newtons). This just happens to exactly equal the weight of the cubic foot or cubic meter of water that is displaced!\n\nIt is this upward water pressure pushing on the bottom of the boat that is causing the boat to float. Each square inch (or square centimeter) of the boat that is underwater has water pressure pushing it upward, and this combined pressure floats the boat.
104409
This is a classic problem from hydrodynamics textbooks. The short answer is, it is approximately simple harmonic motion. You can compute the restoring force caused by the displacement of the liquid if you depress a floating boat (Archimedes principle) and that then, balanced with the weight of the boat, creates the conditions for simple harmonic motion. You can approximate the period and amplitude of motion etc. \n\nHowever it gets more complicated than this of course:\n\na. There are damping forces caused by the motion of the boat through the water and the air\n\nb. The water is not completely incompressible, and the density of the water varies some with depth (a tiny effect)\n\nc. There are surface tension effects and entrainment effects\n\nd. The motion of the boat will be more complicated than simple linear motion in one dimension\n\ne. There will probably be deformation effects on the boat, changing its shape\n\nf. gravity is not constant as the boat is moving up and down a small distance in a gravity gradient\n\nand so on. \n\nHowever, the REASON that sines and cosines are so prevalent everywhere in physics is because simple harmonic motion is such a good approximation for so many things. \n\nWhy is this?\n\nWell consider Newton's Second law: F=ma, where F is force, m is mass and a is acceleration. Newton's second law is not always true, in the quantum world and in relativistic situations, but it is true under many conditions, so it is a good place to start. \n\nIn general, the force F will be some sort of nonlinear function of position x:\n\nF=F(x)\n\nHowever, if x is small, then we can approximate F(x) by a McLaurin series:\n\nF ~ F(0) + x F'(0) + h.o.t. \n\n(h.o.t. is a common acronym for higher order terms).\n\nThis then produces the equation for simple harmonic motion, when substituted into Newton's 2nd law:\n\nF(0) + xF'(0) = m d/dt(d/dt(x))\n\nMany other equations in physics like Schrodinger's equation, or wave equations with forcing, or the heat equation, or the inhomogeneous Laplace's equation include 2nd order derivatives, and can similarly be put in some form where simple harmonic motion is the result. So as strange as it seems when you are just learning about SHM in physics, it really is everywhere in all kinds of unexpected places! \n\n\nOne of my favorites is the waves of heat and cold that are travelling down into the earth from the seasonal forcing produced at the surface. Drilling down, one can observe these waves of hot and cold (with some diffusion) going back many years.
719052
Very very simple. Take a baloon ( white or any light color), blow it to its complete size. Then, tie it at the end so that the air does not go out of the baloon. Then paint on it as the planet should be. Par example, Paint with blue and brown for the planet Earth. If you want to hang it, use a wire.
99038
The Plimsoll line is the mark on the hull of a ship that shows where the waterline is when the ship is loaded to full capacity according to the condition of the water at the point of loading.
60733
simply use a hydrometer.