Many of us at school asked ourselves the question: “How to find body weight”? Now we will try to answer this question.
Finding mass through its volume
Suppose you have a two-liter barrel at your disposal. You intend to completely fill it with diesel fuel, which you use to heat your small boiler room. How to find the mass of this barrel filled with diesel fuel? Let's try to solve this seemingly simplest task with you.
Solving the problem of how to find the mass of a substance through its volume is quite easy. To do this, apply the formula for the specific gravity of the substance
p = m / v,
where p is the specific gravity of the substance;
m is its mass;
v - occupied volume.
Grams, kilograms and tons will be used as a measure of mass . Measures of volumes: cubic centimeters, decimeters and meters. The specific gravity will be calculated in kg / dm³, kg / m³, g / cm³, t / m³.
Thus, in accordance with the conditions of the task, we have at our disposal a barrel of two hundred liters. This means that its volume is 2 m³.
But you want to know how to find the mass. From the above formula, it is derived like this:
m = p * v
First we need to find the value of p - the specific gravity of diesel fuel. You can find this value using the directory.
In the book we find that p = 860.0 kg / m³.
Then we substitute the obtained values into the formula:
m = 860 * 2 = 1720.0 (kg)
Thus, the answer to the question of how to find the mass was found. One ton and seven hundred and twenty kilograms is the weight of two hundred liters of summer diesel fuel. Then you can make the same approximate calculation of the total weight of the barrel and the power of the rack under the barrel with a solarium.
Finding mass through density and volume
Very often, in practical tasks in physics, one can find such quantities as mass, density, and volume. In order to solve the problem of how to find body weight, you need to know its volume and density.
Items you will need:
1) Roulette.
2) Calculator (computer).
3) Capacity for measurement.
4) Ruler.
It is known that objects with an equal volume, but made of different materials, will have different masses (for example, metal and wood). The masses of bodies that are made of a certain material (without voids) are directly proportional to the volume of the objects in question. Otherwise, a constant is the ratio of mass to volume of objects. This indicator is called the "density of matter." We will denote it by the letter d.
Now you need to solve the problem of how to find the mass in accordance with the formula d = m / V, where
m is the mass of the item (in kilograms),
V is its volume (in cubic meters).
Thus, the density of a substance is the mass of a unit of its volume.
If you need to find the density of the material from which the object is created, then you should use the density table, which can be found in the standard textbook on physics.
The volume of the item is calculated by the formula V = h * S, where
V - volume (m³),
H is the height of the item (m),
S is the base area of the item (m²).
In the event that you can not clearly measure the geometric parameters of the body, then you should resort to the help of the laws of Archimedes. To do this, you need a vessel that has a scale that serves to measure the volume of liquids and lower the object into water, that is, into a vessel on which there are divisions. The volume by which the contents of the vessel will be increased is the volume of the body that is immersed in it.
Knowing the volume V and density d of an object, you can easily find its mass using the formula m = d * V. Before calculating the mass, you need to bring all the measuring units into a single system, for example, the SI system, which is an international measuring system.
In accordance with the above formulas, the following conclusion can be made: to find the required mass with a known volume and known density, it is necessary to multiply the density value of the material from which the body is made by the volume of the body.