you need
  • - handle;
  • - pencil;
  • - line;
  • - protractor;
  • - Calculator;
  • - paper records.
in theoretical mechanics forces have treated as a sliding vector.That is, the vector forces can be transferred along the lines on which they are located.Consequently, the directions of the two forces , applied to the body, intersect at point A. If the condition of the problem you need to find resultant two forces, acting on the body along a straight line, the scalar values ​​countervailing forces deducted.A forces , attached in the same direction, added.
Another case - when two s forces act on the body at an angle to each other.To add forces s in this example, you need to know the angle between their vectors.Find resultant forces can graphical and graph-analytic
al method.
How to find
graphical method vectors are added by the rule of parallelogram, or triangle.For example, given two forces s 5,5N and 11,5N, the angle between them is equal to 65o.To find resultant forces , first select the scale of the plotting.For example, 1cm = 1N.Iz point A at an angle of 65o to each other aside vector a, equal to 5.5 cm, and b, equal to 11.5 cm. In the parallelogram draw the vector sum of the two forces .Its length in this scale equals scalar resultant forces s - 14,5N.To add forces s graphical method by the triangle rule, position the start of the second vector in the end of the first.Construct a triangle.The length of the sides in this scale - it is a scalar value of the sum of forces .
How to find
When two forces graph-analytic method, you can not respect the scale of the construction of the drawing.Construct a triangle or a parallelogram similar to step 3. cosine get the side of a triangle or the diagonal of the parallelogram AC: c = (b ^ 2 + a ^ 2-2bc cosb) ^ 1/2;where a, b - two scalars vectors attached forces , b - the angle between them in a triangle.As seen from the drawing, an angle b = 180-a.