Dynamics of Rotational Motion about a Fixed Axis o
o o
o
Only those components of torques , which are along the direction of the fixed axis , need to be considered because the component of the torque perpendicular to the axis of rotation will tend to turn the axis from its position .
This means
We need to consider only those forces that lie in planes perpendicular to the axis . Forces which are parallel to the axis will give torques perpendicular to the axis .
We need to consider only those components of the position vectors which are perpendicular to the axis . Components of position vectors along the axis will result in torques perpendicular to the axis