The forces, whose lines of action are parallel to each other and act in the same directions, are known as like parallel forces.
The three forces of 100N, 200N and 300N have their lines of action parallel to each other but act in the opposite directions. These forces are known as unlike parallel forces.
Two like parallel forces are acting at a distance of 24mm apart and their resultant is 20N. If the lines of action of the resultant is 6mm from any given force, the two forces are 15N and 5N.
If a body is acted upon by a number of coplanar non-concurrent forces, if any
rotate about itself without moving
move in any one direction rotating about itself
be completely at rest
A smooth cylinder lying on its convex surface remains in unstable equilibrium.