A force while acting on a body may

* change its motion

* balance the forces, already acting on it

* give raise to the internal stresses in it

In order to determine the effects of a force, acting on a body, we must know

* magnitude of the force

* line of action of the force

* nature of the force i.e. whether the force is push or pull

In S.I system of units, the unit of force is **Newton** (briefly written as **N**). A Newton may be defined as the force, while acting upon a body of mass 1 kg, produces an acceleration of 1m/s^{2} in the direction of which it acts.

1 N = 1 kg x 1 m/s^{2} = 1 kg-m/s^{2}

One kg force is equal to **9.8 N**.

1Kgf (one kilogram force) is the force exerted by one kilogram mass when it is kept in a gravitational field of magnitude 9.8m/s² .

And force equals to

F=ma

F=1Kg × 9.8m/s²

So 1kgf=9.8N

The algebraic sum of the resolved parts of a number of forces in a given direction is equal to the resolved part of their resultant in the same direction. This is known as principle of resolution of forces.