# BIOMECHANICS APPLICATIONS - Instruct 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

1. Magnitude - product of F x FA 2. Direction - angle of pull on bone 3. Line of Action - vector direction 4. 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 actionperpendicular) to line of action TEETER-TOTTER Axis of Rotation 2 Forces 2 Force Arms FIG E.8

Page 116 of textbook See FIG 9-30 page 296 Basic Biomechanics 4th Edition Susan J. Hall

T = F x FA F is board reaction FA is d t is board recoil time p. 328 in course text

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

See course text FIG E.21 on page 127 FIG E.22 on page 127 C of B is the location of the C of G of the volume of water displaced by a

immersed body There is no T (perpendicular) to line of actiontorque) when the persons CB is aligned with her/his CG When CB is co-linear with CG, the body will float and not rotate