Chapter 12 Measurement of Force C. S. Bahra and J. Paros 12.1 Basic concepts if a body is released, it will start to fall with an acceleration due to gravity or acceleration of free fall of its location. We denote by g the resultant acceleration due to attraction of the earth on the body and the component of acceleration due to rotation of the earth about its axis. The value of g varies with location and height, and this variation is about 0.5 percent between the equator and the poles. The approximate value of g is 9.81 m/s 2 . A knowledge of the precise value of g is necessary to determine gravitational forces acting on known masses at rest, relative to the surface of the earth, in order to establish practical standards of force. Practical standards briefly the principles employed in their design, limitations, and use. it is not intended to give a detailed description of mathematical and physical concepts but provides enough information to allow an interested reader to read further. 12.2 Force measurement methods Force measurement methods may be divided into two cate- gories: direct comparison and indirect comparison. in a direct comparison method, an unknown force is directly compared with a gravitational force acting on a known mass. A simple analytical balance is an example of this method. An indirect