Mathematically speaking, a kilogram of stone is as heavy as a kilogram of cotton.

The density of stone is different from that of cotton. From common sense, the density of stone is much higher than that of cotton, giving the impression that stone is much heavier than cotton. Although a kilogram of stone is as heavy as a kilogram of cotton, the volume of a kilogram of stone is much smaller than that of a kilogram of cotton, which is the difference in density.

After knowing the weights of the two objects, we don't need to look at what they are, but simply compare the weights, that is, from a mathematical point of view, for example, 0.99 kg of iron is lighter than 1 kg of cotton, and 1 0/kg of stone is heavier than1kg of cotton. The same is true for the comparison of the weights of other objects.

Extended data:

Kilogram is the unit of mass, and mass is equivalent to how "heavy" a thing is every day. However, quality is actually an attribute with "inertia"; In other words, an object will tend to maintain its current speed without external force. When an object with a mass of one kilogram is subjected to a force of one Newton, it will get an acceleration of one meter per square second (about one tenth of the acceleration of the earth's gravity).

The weight of matter depends entirely on the local gravitational intensity, while the mass is constant (assuming that the mass does not move relative to the observer at relativistic speed). Accordingly, astronauts in microgravity can lift objects in the space capsule effortlessly; Because objects are weightless. However, an object still maintains its mass in microgravity, and astronauts need to exert ten times the force to accelerate an object with ten times the mass at the same acceleration.