A force is losely described as being a "push" or a "pull". Your everyday experience gives you an intuitive understanding of this definition. A more careful definition includes the statement that a force is a vector quantity; it has magnitide and sence of direction, and the property of being resolvable into tow or more components. As you have learned from your textbook, the most convinient components of a force are those which are perpendicular one to the other; thus, Cartesian (x,y) coordinates are often chosen.
In making measurenmets on a force F, it will be convenient to have the object on which F acts to remain at rest. This will be true only if other forces are also acting on the object in such a way that equilibrium is established. Assume that F and the other forces all act at one point (the are concurrent) and that they are push or pull in the same plane ( they are coplanar ). Then according to the Newton Laws, if the object is to be at rest,its velocity is to be zero, and if its velocity is to remain zero, the components of acceleration must be zero; thus
where m is the mass of the object, 
and 
are the
components of acceleration, and 
is to be read
"sum of the x-components of the forces".
In this Exercise you will measure the magnitudes and directions of a force F, and of forces F1 and F2 which cause the object upon which the forces are acting to be in equilibrium. You will be able to show graphically that Eqn.1 and Eqn.2 are true.
The apparatus used in this exercise provides means of measureing the magnitude and direction of forces. The object on which the forces act is the ring to which strings are tried, and each force is provided by the tension in a string on which are suspended weights which as usual are marked in units of grams. Recall that the force in newtons is obtained by multiplying the mass m in kilograms by the acceleration of gravity, g = 9.80 m/sec2, thus
