Lecture 4 Biomechanical Principles: Newton's 1st Law Flashcards
Newton’s 1st Law of Inertia says
“A body remains at rest or at a constant linear velocity (OR angular velocity around an axis rotation) except when compelled by an external force to change its state”
What is inertia?
amount of energy required to alter the velocity of a body
What is Center of Mass? Human body COM?
point of a body or body segment where mass is evenly distributed in all directions
-human body lies just anterior to 2nd sacral vertebra in upright (anatomical)
Center of gravity
point where effects of gravity are completely balanced
Two types of Linear motion (translational)
curvilinear (curved line) or rectilinear (straight line)
When you walk, a point on the head moves in a general __________ manner
curvilinear
Angular motion is how the ___________ moves
human body
-break down by segments and joint
Mass Moment of Inertia
quantity that indicates resistance to a change in angular velocity
Dependent on mass of the body but also the distribution of mass with respect to the _____________
axis of rotation
Distance of _____ changes in relation to the axis of rotation of the ______
- COM
- joint
When distance of COM changes, this changes the ______ of inertia of the limb
mass moment
R leg extended has ________ mass moment of inertia than L leg in take off stance (pic on slide 6)
greater
In swing phase, limb shortens which _______ mass moment of inertia and _______ torque required by hip muscles to accelerate or decelerate limb
- reduces
- decreases
Example of smaller Mass Moment of Inertia
can be achieved by moving a cuff weight from the wrist to the mid-forearm
Mass moment of intertia can be controlled by changing…
the position of the body
