Notes on systems of parallel forces
With systems of forces acting on a particle, it follows that all the forces have a line of action passing through the same point, which is the particle. In such cases, if the system is not in equilibrium, we can find a single resultant force which also acts through the same point and we can state the magnitude and direction of this resultant. There is no turning effect because all the forces, including the resultant, have zero perpendicular distance of their line of action from the object being considered, (the particle).
If we have a system of forces which do not all pass through the same point, then if the system is not in equilibrium, we must find a resultant force and specify its magnitude and direction as before, but we must also state where its line of action is positioned. There are now many different possible arrangements of forces, so let's simplify by considering some of the general possibilities.
First let's consider the type of situation where all the forces are parallel to each other, though they might be in opposite directions. In each case we will consider the forces to be acting on a light rod.
What if there's only one force?
[I'm still working on these notes. When they are finished there will be a diagram here.]
Obviously, the system cannot be in equilibrium unless the force is zero. This is the trivial case and if it is not zero, then the resultant force is just the same as the given force.
What if there are two forces?
[I will be finishing this later]
If we have a system of forces which do not all pass through the same point, then if the system is not in equilibrium, we must find a resultant force and specify its magnitude and direction as before, but we must also state where its line of action is positioned. There are now many different possible arrangements of forces, so let's simplify by considering some of the general possibilities.
First let's consider the type of situation where all the forces are parallel to each other, though they might be in opposite directions. In each case we will consider the forces to be acting on a light rod.
What if there's only one force?
[I'm still working on these notes. When they are finished there will be a diagram here.]
Obviously, the system cannot be in equilibrium unless the force is zero. This is the trivial case and if it is not zero, then the resultant force is just the same as the given force.
What if there are two forces?
[I will be finishing this later]