UNITS AND DEFINITIONS RELATED TO BIOMECHANICAL AND ELECTROMYOGRAPHICAL MEASUREMENTS - Biomechanics and Motor Control of Human Movement - page 364

TABLE B.2 (Continued)

Name of

Physical Quantity Symbol SI Unit Definition

Young's modulus
Shear modulus

E
G

Pa Ratio of stress to strain over the

initial linear portion of a
stress - strain curve.

Wor k W joule (J) Energy change over a period of

time as a result of a force
acting through a displacement
in the direction of the force. 1 J
is the work done when a force
of 1 N is displaced a distance
of 1 m in the direction of the
force (1 J m.). Work is

also the time integral of power.
(1 J

= 1N ·

= 1W · s.).

Mechanical energy E J Capacity of a rigid body to do

work; quantified by the sum of
its potential and kinetic
energies.

Potential energy V J Energy of a mass or spring

associated with its position or
configuration relative to a
spatial reference.
Gravitational potential energy of
amass m raised a distance h
above the reference level
equals mgh ,where g is the
acceleration from gravity.
Elastic potential energy of a
linear spring with stiffness k
stretched or compressed a
distance e equals k e 2 /2. ·

Kinetic energy T J Energy of a mass associated with

its translational and rotational
velocities. The translational
kinetic energy T of a mass m
with a velocity v is 1/2 mv 2 .
The rotational kinetic energy T
of a body rotating in a plane
with a moment of inertia I
rotating with a angular velocity
ω is 1/2 I ω 2 .