ABSTRACT
A rigid body is free to rotate about a fixed axis. A force, → F , with magnitude F and direction
F̂ , acts on the body at the point labelled P , as illustrated in Figure 39.1.
P
→ F
−−→OP
FIGURE 39.1 A Force Applied at a Point on a Rigid Rotating Body
The vector −−→OP resides in a plane perpendicular to the axis of rotation and extends from
the axis to the point P . The applied force has a component parallel to −−→OP , dubbed F‖. The remaining part(s) of the force vector, having vanishing projection onto
−−→OP , have magnitude F⊥ and lie entirely in the plane perpendicular to
→ F‖
→ F⊥→F
−−→OP P
θ
FIGURE 39.2 Vector Decomposition of a Force Acting at a Point
39-259
of
→F [when placed 2], is employed to express the
parallel and perpendicular components of the force:
F‖ = F cos(θ) , and F⊥ = F sin(θ) .
