Biomechanics Principles Flashcards
Define the law of inertia
- resistance to change in linear velocity
- all objects have it
- all changes in linear motion must overcome it
Newton’s 1st law
body at rest (or constant velocity) doesn’t change unless acted upon by external force (or torque)
- an object at rest will stay at rest unless acted upon
Newton’s 2nd law
acceleration of a body is proportional to the force (or torque) causing it, occurs in the direction of application, and is inversely proportion to its own mass
- F = m x a
Newton’s 3rd law
all forces (or torques) have equal, and oppositely directed, forces (or torques)
- all actions have an equal and opposite reaction
Define center of mass (COM)
point at which mass is evenly distributed/balanced
Where is the center of mass (COM) located for the total body
anterior to 2nd sacral vertebra
Define base of support (BOS)
contact perimeter of the area of reaction force application (ex: in standing, boundary containing the feet or other limb/device)
Define mass moment of inertia
the rotational analog of inertia (I = m x ρ^2)
Define acceleration
the rate of change of velocity
Equation for Newton’s 2nd law for rotational
T = I x α
Equation for momentum
p = m x v
Equation for impulse linear and rotational
Linear: F x t = m x Δv
Rotational: T x t = I x Δω
Define impulse
change in momentum
Equation for work
Work = Force x Displacement
Equation for potential energy
PE = m x g x h
Equation for linear and angular kinetic energy
KE Linear = 1/2 x m x v^2
KE Angular = 1/2 x I x ω^2
Equation for power
Power = Work / Time
Define anthropometrics
the measurement of humans
Purpose of a free body diagram
shows interaction between body and its environment
Define global/laboratory reference frames/coordinate frames
refers to an external, world-based, non-moving coordinate system
Define local/relative reference frames/coordinate frames
- a coordinate system attached to a segment
- move with respect to world and other segments
