When several forces of different magnitude and different direction act upon a certain body, they constitute a system of forces.
If all the forces in a system lie in a single plane, it is called a coplanar force system.
If the line of action of all the forces in a system passes through a single point it is called a concurrent force system.
In a system of parallel forces, all the forces are parallel to each other.
If the line of action of all forces lies along a single line, then it is called a collinear force system.
The various system of forces, their characteristics and examples are given in the table below.
Table: System of Various Forces
| S.No | Force System |
Characteristic
|
Examples
|
|---|---|---|---|
| 1 | Collinear forces | Line of action of all the forces acts along the same line. | Forces on a rope in a tug of war. |
| 2 | Coplanar parallel forces | All forces are parallel to each other and lie in a single plane. | The system of forces acting on a beam subjected to vertical loads. |
| 3 | Coplanar like parallel forces | All forces are parallel to each other, lie in a single plane and are acting in the same direction. | The weight of a stationary train on a rail when the track is straight. |
| 4 | Coplanar Concurrent forces | Line of action of all forces pass through a single point and forces lie in the same plane. | Forces on a rod resting against a wall. |
| 5 | Coplanar Non-concurrent forces | All forces do not meet at a point but lie in a single plane. | Forces on a ladder resting against a wall when a person stands on a rung which is not at its centre of gravity. |
| 6 | Non-coplanar parallel forces | All the forces are parallel to each other, but not in the same plane. | The weight of benches in a classroom. |
| 7 | Non-coplanar concurrent forces | All the forces are parallel to each other, but not in the same plane, but their lines of action pass through a single point. | A tripod is carrying a camera. |
| 8 | Non-coplanar non-concurrent forces | All forces do not lie in the same plane, but their lines of action pass through a single point. | Forces are acting on a moving bus. |
