Biomechanical Principles Flashcards
Newton’s First law is what?
Law of Inertia:
Body remains at rest or constant linear/angular velocity except when compelled by an external force to change its state
What is inertia?
amount if energy required to alter velocity of a body
What is inertia directly related to?
Directly proportional to mass
What is center of mass?
Point of body or segment where mass is evenly distributed in all directions
Where is center of mass typically located on human body?
Just anterior to 2nd sacral vertebra in upright
What is meant by center of gravity?
Point where effects of gravity are completely balanced
What is mass moment of inertia?
Quantity that indicates resistance to a change in angular velocity
What is the mass moment of inertia dependent on?
On mass of the body but also the distribution of mass with respect to axis of rotation
Which is easier to move forward during swing phase of gait:
- 40 lb leg that is flexed at hip and knee
- 40 lb leg extended at hip and knee
- When limb shortens (flex) -> reduces mass moment of inertia and decreases torque required by hip muscle ti accelerate or decelerate limb
- Extend leg = has greater mass moment of inertia
What is Newton’s Second Law?
Law of acceleration:
Linear acceleration of a body is directly proportional to the force causing it, takes place in the same direction in which the force acts and is inversely proportional to the mass of the body
What is acceleration directly proportional with?
Force
What is acceleration inversely proportional to?
Mass
What is angular acceleration directly proportional with?
torque
What is angular acceleration inversely proportional to?
mass of moment of inertia of body
What is Newton’s third law?
Law of Action-Reaction
For every for there is an equal and opposite directed force
