Weight — very important physical quantity. The modern physics considers it as characteristic of gravitational and inert properties of an object. If you know the surface area of any body, can learn also its weight.

## It is required to you

- - calculator.

## Instruction

1. To find body weight, it is necessary to increase its volume by density which can be learned in reference books. In figure 1 density of widespread substances are presented. Notice that sizes are specified at a certain temperature i.e. if you want to find the mass of the cooled or heated substance, you should consider it when calculating.

2. It is necessary to find volume. That the area is known you can find volume on standard formulas for various geometrical figures. So, the volume of a direct parallelepiped is equal to the work of the area of its basis on height. The volume of a sphere can be found, having divided the area of the sphere built in degree 3/2 into the work by six and a root square of π. Cone volume — having divided the work of the area of the basis of a cone and its height into three. Cylinder volume — having increased the area of the basis of a cylinder by its height.

3. Apparently, only in a case with a sphere it is possible to remove a formula in which the area of its surface is used only, in other cases additional parameters are necessary. For overcoming this difficulty you are come to the rescue by a cube. All his edges have equal length therefore the total area of a surface is equal 6*a^2. From here, on the known area, you can find edge length, it will be equal to a root square of S/6 where S is the total area of a surface of a cube. Now you can find cube volume, having built the turned-out edge length the third degree.

4. Knowing the surface area of a certain figure, you can present a cube with just the same surface area and find its volume as it was shown above. It will be equivalent to body volume with this surface area.

5. Thus, knowing the surface area even of very difficult figure, you can always reduce finding of its volume to finding of volume of a cube of the equal area. Then it is possible to find weight, having increased the received value by substance density. Of course, such method will have a considerable error, but you will be able to learn the approximate mass of an object.