Chapter 14 Angular Kinetics of human movement (KNES 361)

What is moment of inertia?

(Resistance to Angular Acceleration) 

The inertial property for rotating bodies represents resistance to angular acceleration based on both mass and distance the mass is distributed from the axis of rotation

What is the radius of gyration? 

• Distance from the axis of rotation to a point where the body’s mass could be concentrated without altering its rotational characteristics 

• Used as the index for mass distributions for calculating moment of inertia: 

I = mk²

What is angular momentum?

• Quality of angular motion possessed by a body 

• Measured as the product of moment of inertia and angular velocity 

What is the principle of conversation of angular momentum? 

The total angular momentum of a given system remains constant in the absence of external torques 

What produces change in angular momentum?

Angular impulse- The product of torque and the time interval over which the torque acts:

What is the angular law of inertia?

A rotating body will maintain a state of rest or constant rotational motion unless acted on by an external torque that changes the state

What is the angular law of acceleration?

A net torque causes angular acceleration of a body that is 

• of a magnitude proportional to the torque

• in the direction of the torque 

• Inversely proportional to the body’s moment of inertia 

What is the angular law of reaction?

• For every angular action, there is an equal and opposite angular reaction

• When one body exerts a torque on a second, the second body exerts a reaction torque that is equal in magnitude and opposite in direction on the first body