Biomechanical Principles Flashcards
What is Newton’s 1st Law? What does it state?
Law of inertia
“A body remains at rest or at a constant linear velocity except when compelled by and external force to change its state.”
“A body remains at rest or at a constant angular velocity around an axis of rotation unless compelled by and external torque to change its state.”
Define inertia.
An objects resistance to change in its state.
To overcome it, a force is required.
Inertia is directly proportional to mass.
What is the center of mass?
A point of a body or body segment where mass is evenly distributed in all directions.
Where does the center of mass lie in the human body?
Just anterior to the 2nd sacral vertebra in the upright position.
What is the center of gravity?
A point where effects of gravity are completely balanced.
What is the center of pressure?
The point where the most force from the body is in contact with the ground.
Follows center of mass to help maintain upright posture.
Define moment of inertia.
Quantity that indicates resistance to a change in angular motion.
Is dependent on mass of the body but also the distribution of mass with respect to the distance from the axis of rotation.
What can control the moment of inertia?
Changing the position of the body.
*Decreased moment of inertia increase angular velocity
What is Newton’s 2nd Law? What does it state?
Law of acceleration.
“The 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.
“The angular acceleration of body is directly proportional to the torque causing it, takes place in the same rotary direction in which the torque acts and is inversely proportional to the moment of inertia of the body.”
What is Newton’s 3rd Law? What does it state?
Law of action-reaction.
For every force, there is an equal and opposite force.
What is a kinetic chain?
It describes the human body as a series of interrelated segments. The movement of one segment affects movements proximal and distal.
What is the kinetic link principal?
The summation and continuity of segment velocity.
What are 3 ways to objectively measure human movement?
- Electrogoniometer = measures joint angular rotation during movement.
- Accelerometery = measures acceleration of either individual segment or whole body.
- Motion capture = photography and videography
What are 3 kinetic measurement systems?
- Mechanical device = dynamometer
- Transducer = force plate
- Electromechanical devices = isokinetic dynamometer
