TORQUE DEFINED

1. 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

2. 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

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

4. TEETER-TOTTER • Axis of Rotation • 2 Forces • 2 Force Arms

5. FIG E.8 Page 116 of textbook

6. See FIG 9-30 page 296 “Basic Biomechanics” 4th Edition Susan J. Hall

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

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

9. 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

10. 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

11. 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

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

13. 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 (torque) when the person’s CB is aligned with her/his CG • When CB is co-linear with CG, the body will float and not rotate