How to Calculate Floating Force: 12 Steps (with Photo) - tips

Video: Bouyancy: Calculate Submerged Depth of a Floating Block

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Floating force is the force acting on an object submerged in fluid in the opposite direction to gravity. When an object is placed in a fluid, the object's weight pushes down the fluid (liquid or gas) while the buoyancy pushes the object upwards, in the opposite direction of gravity. In general, this buoyancy can be calculated using equations F_b = V_S × D × g, in which F_b is the buoyancy, V_S is the volume of the submerged part, D is the density of the fluid surrounding the object, and g is the gravity. To learn how to determine the buoyancy of an object, start with Step 1 below.

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Method 1 of 2: Use the floating force equation

Find the volume the submerged part of the object. The floating force acting on the body is directly correlated with the submerged volume portion of the object. In other words, the larger the sink of a solid body, the stronger the buoyancy is acting on it. That is, even if the object is completely submerged in the liquid, there is still a buoyancy acting on it. To begin calculating the buoyancy force acting on an object, the first step is usually to determine the volume of volume that is soaked in the fluid. In the equation for the floating force, this value must be written in m.
- For an object completely submerged in the fluid, the volume that is submerged will be equal to the volume of the object itself. For floating objects on the surface of the fluid, we only consider the volume fraction below the surface of the fluid.
- For example, let's say we want to find the buoyancy acting on a rubber ball floating in water. If the ball is a perfect sphere 1 m in diameter and it floats with exactly one half submerged, we can find the volume of the submerged part by calculating the volume of the entire ball and dividing it in half. Since the volume of the sphere is (4/3) π (radius), we have the volume of the ball to be (4/3) π (0.5) = 0.524 m. 0.524 / 2 = 0.262 m was sunk.
Find the density of the fluid. The next step in finding floating force is to determine the density (in kg / m) of the surrounding liquid. Density is a quantity measured by the ratio of the mass of a matter or matter to its corresponding volume. With two objects of equal volume, the object with a higher density will be heavier. The general rule of thumb is that the higher the density of a fluid, the greater the buoyancy will exert on the body that sinks in it. With fluids, usually the easiest way to determine density is through references.
- In the example above, the ball floats in the water. Reference study literature tells us that water has a specific density 1,000 kg / m.
- Density of many common fluids is given in the technical literature. You can find this list here.
Find gravity (or another force downward). Whether an object sinks or floats in a fluid, it is always under the force of gravity. In fact, this downward force constant is about 9.81 Newtons / kilogram. However, in cases where there is another force acting on the fluid and the body sinking in it such as the radial force, we must also consider this force when calculating the total "downward" force for the whole system.
- In the above example, if we have a normal static system then it can be assumed that the only downward force acting on the fluid and the body is the standard gravity - 9.81 Newtons / kilogram.
Multiply volume by density and gravity. When you have the values for the object volume (in m), the fluid density (in kg / m), and the gravity (or the downward force of the Newton / Kilogram system), finding the floating force becomes easy. . Simply triple these to find the floating force in Newtons.
- Solve the example problem by plugging the values into the equation F_b = V_S × D × g. F_b = 0.262 m × 1,000 kg / m × 9.81 N / kg = 2,570 Newtons. The other units would annihilate each other, leaving only the Newton unit.
Determine if the object is floating or not by comparing with gravity. Using the equation for buoyancy, you will easily find the force that pushes the object out of the liquid. However, you can also determine if the material floats or sinks in the fluid if you take one extra step. Find the floating force acting on the whole body (that is, use the entire volume of body V_S), then find the gravity that attracts the object by the equation G = (mass of the object) (9.81 m / s). If the floating force is greater than the gravity, the object will float. On the other hand, if the gravity is greater then the object will sink. If these two forces are equal then we say the thing suspended.
- A suspended object will not float above water or sink to the bottom while in water. It will be suspended in the liquid between the surface and bottom.
- For example, let's say we want to know whether a 20 kg cylindrical wooden crate with a diameter of 0.75 meters and a height of 1.25 meters can float in water. We must perform several steps for this problem:
  - The first is to find volume by using the formula for cylinder volume V = π (radius) (height). V = π (0.375) (1.25) = 0.55 m.
  - Next, assuming we know the standard gravity and the density of the water, we solve for the floating force acting on the barrel. 0.55 m × 1000 kg / m × 9.81 N / kg = 5,395.5 Newton.
  - Now we have to find the gravity acting on the wooden crate. G = (20 kg) (9.81 m / s) = 196.2 Newton. This result is much smaller than the buoyancy force, so the barrel will float.
Use the same calculation when the fluid is a gas. When solving problems with buoyancy, don't forget that the fluid doesn't have to be a liquid. Gases are also known as fluids, although they have a very small density compared to other types of matter, and gas can still repel some of the floating objects in it. The helium bubble is the proof of this. Since the helium in a bubble is lighter than the fluid around it (air), the bubble will fly away! advertisement

Method 2 of 2: Perform simple experiment on floating force

Place a small bowl in a larger one. With just a few objects in the house, you will easily see the effects of buoyancy in practice. In this experiment, we show that when an object is submerged, it will suffer the effect of the buoyancy, because it takes the place of the amount of fluid that is equal to the volume of the submerged object. In the process of doing experiments we also show how to find the floating force of the object in practice. First you place a small, capless container, such as a bowl or cup, in a larger container such as a large bowl or bucket of water.
Fill a small, edge-to-edge container with water. You must pour the water close to the edge without spilling it. Be careful at this step! If you let the water overflow, you must empty the large container completely and start over.
- For this experiment, we assume water has a density of 1000 kg / m. Unless you use brine or an entirely different liquid, most waters have a density close to this reference value so the results will not be affected.
- If you have a dropper, you can use it to drip water into the inner container so the water level is up to the edge.
Immerse a small object. Next, look for an object that can fit comfortably in a small container with no water damage. Find the weight in kilograms of this object (you should use the scale for the reading in grams and then convert it to kilograms). Then slowly press the object into the water without getting your finger wet until it starts to float or you can barely hold it, and then release the object. You should see some water spill over the edge of the inner container into the outer container.
- For this example, let's say we are pressing a 0.05 kg toy car into its inner container. We don't need to know the volume of the car to calculate the buoyancy, as we'll know in the next step.
Collect and measure the water overflow. When you press an object into the water, it takes the place of some water - otherwise there is no space for you to immerse it in the water. When it pushes water out of the path, the water repels and creates buoyancy. Collect the spilled water from the inner container and pour it into the small measuring cup. The volume of water in the beaker should be equal to the volume of the submerged object.
- In other words, if the object floats, the volume of water overflowing will be equal to the volume of the object submerged under the water's surface. If the object sinks, the volume of water overflow will be equal to the volume of the entire object.
Calculate the amount of water spilled. Since you know the density of water and can measure the volume of water overflowing in a measuring cup, you will calculate the volume of water. Convert the volume to m (an online unit converter like this one can help here) and multiply it by the density of water (1,000 kg / m).
- In the example above, assume the toy car is submerged in its inner container and occupies about 2 tablespoons (0.00003 m) of water. To find the mass of water, multiply this by density: 1,000 kg / m × 0.00003 m = 0.03 kg.
Compare the volume of displaced water and the mass of the object. Now that you know the masses of both the submerged and the displaced water, compare these two values. If the mass of the object is greater than the volume of the displaced water, the object will sink. On the other hand, if the volume of the displaced water volume is greater then the object will float. This is the principle of buoyancy in practice - for a floating body it must displace a mass of water greater than the mass of the body itself.
- Hence the light masses but the large volumes are the best floating objects. This property indicates that hollow objects can float very well. Let's take a look at the canoe - it floats well because it's hollow inside, so it can take up a lot of water but the mass isn't too heavy. If the canoe was thick inside it wouldn't be able to float well.
- In the example above, a vehicle with a mass of 0.05 kg is greater than a volume of water displaced by 0.03 kg. This is in line with what we observe: the car has sunk.
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