The meaning of the center of gravity of an object in physics

Definition: All parts of an object are subject to gravity. In terms of effect, we can think that the gravitational force on each part is concentrated in one point, which is called the center of gravity of the object.

The position of the center of gravity of an object, an object with a uniform distribution of mass (a homogeneous object), and the position of the center of gravity is only related to the shape of the object. For example, the center of gravity of a uniform thin straight rod is at the midpoint of the rod, the center of a uniform sphere is at the center of the sphere, and the center of gravity of a uniform cylinder is at the midpoint of the axis. The center of gravity of an irregular object can be determined by the suspension method.

The center of gravity of an object, not necessarily on the object.

In the case of an object with uneven mass distribution, the position of the center of gravity is not only related to the shape of the object, but also to the distribution of mass within the object. The center of gravity of a truck changes with how much is loaded and where it is loaded, and the center of gravity of a crane changes with the weight and height of the object being lifted.

If a line or slice of the center of gravity divides an object or figure into two parts, the volume or area of the two parts is not necessarily equal. (Not all lines or slices that pass through the center of gravity divide the area or volume of an object or figure, for example, a straight line that passes the center of gravity of a regular triangle and parallels divides the triangle into two parts with an area ratio of 4:5.)

This can be explained by the principle of leverage in physics: the distance from the center of gravity of the two graphs divided into the center of gravity of the triangle is equivalent to the two arms of the lever, and the area of the two figures is equivalent to the two forces of the lever. Because the center of gravity is equivalent to the point where the area of two figures is "concentrated" into a point (see the definition of center of gravity).

As in the example above, the distance from the center of gravity of the two shapes to the center of gravity of the triangle is exactly equal to 5:4. If you are interested, you can use the Geometry Artboard software to draw proof.

Mathematically determining the position of the center of gravity of an object:

In the space where an object (total mass is m) is located, take any definite spatial Cartesian coordinate system o-xyz, then the object can be derived from i particles, each of which corresponds to its own coordinates (xi, yi, zi) and mass mi, it is easy to know m=m1+m2+ +mi, and let the center of gravity of the object be g(x,y,z).

then x=(x1m1+x2m2+ +ximi) m

y=(y1m1+y2m2+¨+yimi)/m

z=(z1m1+z2m2+¨+zimi)/m

The center of gravity is the place where all the forces on the object can be concentrated to one point.

The center of gravity of the object is (the point at which the gravitational force is applied to the slag grip part of the object).

The object makes the following sentence:

1.Reality is made up of two imperfect objects that produce happiness in the fusion and collision of imperfections that collide side by side.

2.Starting with bacteria and single cells and ending with humans, every organism has a perceptible boundary that marks where it begins and ends.

3.A person climbs the rod upwards at a constant speed, imagining that the contact surface light scatters the beam and slips, and the person has a tendency to slide downward relative to the rod, and the direction of the static friction force on the object is the same as the direction of movement of the person.

4.Phagocytic cells in humans and other animals are divided into full-time and non-full-time, and the difference between the two lies in the obvious degree of phagocytic effect.

The position of the center of gravity of the object, the mass of the object is evenly distributed, and it is only related to the shape of the object.

The center of gravity is the point at which the resultant force of all the constituent fulcrums of the gravity force passes through the object in any direction in the gravitational field. The center of gravity of a regular and uniform object is its geometric center. The center of gravity of an irregular object can be determined by the suspension method.

The center of gravity of an object, not necessarily on the object.

The point at which the resultant force of gravity on each part of the object is applied. Every tiny part of an object is subject to gravity (see Gravitational Force), which can be approximated as a system of intersecting forces at the center of the Earth. Since the size of an object is much smaller than the radius of the Earth, the gravitational force acting on an object in general can be approximated as a parallel force system, and the total weight of the object is the resultant force of these gravitational forces.

If the volume and shape of an object are constant, the gravitational force on the object will always pass through a determined point in the coordinate system fixed to the object, i.e., the center of gravity, regardless of the direction the object is in to the ground. The center of gravity is not necessarily on the object, for example the center of gravity of a ring is not on the ring, but on its center of symmetry.

The position of the center of gravity is of great significance in engineering. For example, for the crane to work normally, its center of gravity position should meet certain conditions, and the floating stability of the ship is also related to the position of the center of gravity; If the center of gravity of a high-speed rotating machine is not on the axis, it will cause violent vibrations, etc.