Angular Kinematics of Human Movement Study Guide

Angular Kinematics

The study of the rotation of body segments around joints.

Joint Angles

Measured from anatomical position (straight, fully extended = 0°). Angles are based on segment movement away from this position.

Body Segment Orientation

Angular orientation of a body part relative to a fixed reference (usually horizontal or vertical).

Instant Center of Rotation

The exact point of rotation at a joint at any given moment.

Angular Displacement

The change in angular position or orientation of a body segment.

Angular Displacement Formula

Δθ=θf−θi

Angular Displacement Units

Measured in degrees, radians, or revolutions.

Angular Displacement Direction

Measured as counterclockwise (+) or clockwise (-).

Radian

A unit of angle measure. One radian is the angle subtended at the center of a circle by an arc equal to the radius.

Angular Velocity

The rate of change in angular position.

Angular Velocity Formula

ω=Δθ/Δt

Angular Velocity Units

Degrees per second, radians per second, revolutions per second.

Angular Acceleration

The rate of change in angular velocity.

Angular Acceleration Formula

α=Δω/Δt

Angular Acceleration Units

Degrees/sec², radians/sec².

Linear and Angular Displacement Relationship

The greater the radius of rotation, the greater the linear distance traveled by a point on a rotating body.

Linear and Angular Displacement Formula

s=rθ

Moment of Inertia (I)

The resistance to angular acceleration. Affected by mass and how far the mass is from the axis of rotation.

Radius of Gyration (k)

The distance from the axis of rotation to a point where the body's mass could be concentrated without altering its rotational properties.

Radius of Gyration Formula

I=∑mk²

Angular Momentum (H)

The quantity of angular motion a body possesses.

Angular Momentum Formula

H=Iω

Conservation of Angular Momentum

The total angular momentum of a system remains constant if no external torque acts on it (e.g., in a vacuum).

Angular Impulse

The product of torque and the time interval over which the torque acts. It causes a change in angular momentum.

Angular Impulse Formula

T⋅t=ΔH

Centripetal Force

The force directed toward the center of rotation for a body in rotational motion.

Centripetal Force Formulas

Fc=mv²/r and Fc=mrω²