TORQUE DEFINED a Force applied a system restricted to moving in a circular path causes a system/body to rotate the Point of Application is eccentric T = F x FA

MUSCLE TORQUES Magnitude - product of F x FA Direction - angle of pull on bone Line of Action - vector direction Point of Application - attachment to bone

FA: FORCE ARM shortest distance from axis of rotation to the line of action of the applied Force  (perpendicular) to line of action

TEETER-TOTTER Axis of Rotation 2 Forces 2 Force Arms

FIG E.8 Page 116 of textbook

FIG 9-30 “Basic Biomechanics” 3rd Edition Susan J. Hall

CALCULATING TORQUE Force measured in Newtons [4.45N = 1Lb.] Force Arm measured in meters Torque measured in Newton meters [Nm]

FIG E.11 page 118 sum up all Torques on each side of axis side of axis with the larger  of T determines direction of movement

Angular Motion Vectors there are both kinetic and kinematic vectors A vector is represented by a straight line arrow symbol the length of the arrow is the magnitude the orientation of the arrow is the direction to get a straight line vector for angular motion, the right hand thumb rule is used

RIGHT-HAND THUMB RULE method of determining vector direction for angular motion curve fingers of right hand in the direction of the Torque right thumb points in vector direction of the motion,  to the actual direction of the spin

Right-Hand Thumb points in vector direction FIG 15.9 on page 506 FIG 15.10 on page 507

CENTER of BUOYANCY the location of the C of G of the volume of water displaced by a immersed body body’s CB must be aligned with body’s CG for floating to occur