Kinesiology Chapter 6

rotation

what occurs when the system is restricted to move around a fixed axis and therefore in a circular path

angular motion

rotation is also called

point of application

linear and angular motion differ in the ____ ___ _______ of the force

centric force

force directed through the center of the object; has a line of action that passes through the center of mass

eccentric force

force applied in such a way that the line of action does not pass through the center of mass

torque

the tendency of an eccentric force to rotate an object around an axis

axis of rotation

the point around which a body rotates

magnitude and distance

what are the two factors torque depends upon

force arm

the perpendicular distance between the axis of rotation and the line of action of the applied force

greater

the greater the amount of torque acting at the axis of rotation, the ____ the tendency for rotation to occur

vector

torque is a _____ quantity

positive

a torque that causes a counterclockwise rotation is

negative

a torque that causes a clockwise rotation is

center of mass

the point at the intersection of the three cardinal planes that represents the average location of a system’s mass

displacement

change in position

velocity

change in position relative to the interval in which it takes place

acceleration

change in velocity relative to the interval in which the change takes place

angular distance

the sum of all angular changes undergone by a rotating body

degrees, revolutions, and radians

what are the three units of measure used to represent angular distance and displacement

57.3

how many degrees is in one radian

angular speed

the scalar rate of angular motion

angular velocity

the vector rate of angular motion

angular acceleration

a change in magnitude and/or direction of the angular velocity vector with respect to time

centripetal acceleration

acceleration caused by a change in direction of the velocity vector

center

centripetal force is a what-seeking force

intertia

the resistance of a system to having its state of motion changed by the application of a force

resist

the natural tendency of a system is to _____ change in motion

rotational inertia

the resistance of an object having its state of angular motion changed

moment of inertia

the mathematical relationship of mass, mass distribution, and rotational inertia

mass

rotational inertia is dependent of the system’s

easier

the more closely mass is distributed to the axis of rotation, the ____ it is to initiate or stop angular motion

radius of gyration

the average distance of an object’s mass from the axis of rotation

moment of inertia

the tapering of human limbs keeps most of the limb mass closer to the axis of rotation, which keeps the ______ ____ ______ of the limbs as small as possible

maximize, minimizing

the most efficient way to move the human body is to ______ acceleration while _______ torque requirements

angular momentum

angular motion possessed by a body or system

distribution of mass from the axis of rotation or the angular velocity

since mass doesn’t change, most changes in angular momentum are due to the

torques

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

angular impulse

the product of applied torque and the interval of force application

rotational work

performed when an object is angularly displaced about an axis by the application of a torque

rotational power

term used to express the amount of angular mechanical work performed in a given interval

rotational kinetic energy

energy associated with angular motion