How to define the center of gravity of a flat figure

How to define the center of gravity of a flat figure

As a flat figure it is possible to take the sheet of dense paper or cardboard of a form necessary to you. The main thing that the body was rather thin. In geometry and physics at uniform gravitational field usually understand the center of masses, or the center of inertia as the center of gravity.

It is required to you

  • - flat figure;
  • - pencil;
  • - ruler;
  • - not ground pencil;
  • - threads;
  • - needle.


1. Try to define the center of gravity of a flat figure by practical consideration. Take the new not ground pencil, put it vertically. From above on it place a flat figure. Note a point in which it keeps on a pencil steady on a figure. It will also be the center of gravity of your figure. Instead of a pencil it is possible to use the forefinger which is simply extended up. But it is more difficult, it is necessary to achieve that the finger stood exactly, was not shaken and did not shiver.

2. For demonstration of the fact that the received point is also the center of masses do in it a needle a small hole. Pass a thread throughout an opening, on one of the ends tie a small knot − so that the thread did not jump out. Holding other end of a thread, suspend a body on it. If the center of gravity is defined truly, the figure will be located exactly, parallel to a floor. Its sides will not be shaken.

3. Find the figure center of gravity in the geometrical way. If you gave a triangle, construct in it medians. These pieces connect triangle tops to the middle of the opposite side. The point of intersection of medians will become the center of mass of a triangle. To find a median point of the party, it is possible even to put a figure in half, but consider that at the same time the uniformity of a figure will be broken.

4. If you gave a parallelogram, draw in it diagonals. They will be crossed just in the center of masses. Special cases of a parallelogram: rectangle, square, rhombus. Principle of geometrical search of the center of gravity of such figures similar.

5. Compare the results received geometrical and by practical consideration. Draw conclusions on the experiment course. Small errors are considered as norm. They are explained by not ideality of a figure, inaccuracy of devices, a human factor (small flaws in work, imperfection of a human eye, etc.).

Author: «MirrorInfo» Dream Team