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

• 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 persons CB is
  aligned with her/his CG
• When CB is co-linear with CG, the body will float
  and not rotate

See course text FIG E.21 on page 127 FIG E.22
on page 127