Newton's Laws of Motion: Newton's Laws describe how objects move when subjected to external forces. FBDs are often used in conjunction with these laws.
Equilibrium: Equilibrium refers to a state where the net force on an object is zero, meaning it is either at rest or moving with constant velocity.
Tension: Tension is the force transmitted through a string, rope, or cable when it is pulled at both ends. It can be represented by an arrow in an FBD.