6. Angles Flashcards
What is an Angle?
The space between two intersecting lines or surfaces at or close to the point where they meet
If we wanted to identify the angle at the elbow joint, what information would we require first?
What is a Relative Angle?
A relative angle is the space between the longitudinal axes of adjacent segments (i.e., the angle at a joint)
What is an External Angle?
What is an Internal Angle?
External Angle:
- formed on exterior surface of the joint
Interior Angle:
- formed inside the joint
What is an Absolute Angle?
An absolute angle is the space between a body segment with respect to a fixed line of reference
Which method is better when measuring angles?
a) Using relative angles
b) Using absolute angles
c) Depends on the situation
c) Depends on the situation
What is a Degree º?
Common method for measuring angles
An arbitrary unit of measurement
Useful to ancient astronomers
Once around the circle is 0° to 360°
What is a Revolution (rev)?
Simple and natural measurement
Once around the circle
1 full turn
What is a Radian (rad)?
What is 1 rad equal to?
1 radian = the relationship b/w the length of a line and the angle that is formed
ratio = Length / Angle
1 rad = 57.3º
What are the relationships b/w degrees, revolution and radians? ( º , revs, rad)
360º = 1 revolution
1 revolution = 2π·rad
2π rad = 360º
1 rad = 57.3º
If a wheel rotates 7.25 revolutions, how many radians did it complete?
1 rev = 2π rad
7.25 rev = 7.25 · 2πrad
7.25 rev = 45.5 rad
What is used to meaure angles?
A goniometer is an instrument that measures an angle
Gonia (angle) Metron (measure)
How do joints / body angles differ from normal angles?
The axis of rotation is usually in a fixed position
However, the axis of rotation at a joint is not fixed
What is an Instant Center?
An Instant Center is the point around which a body or object rotates at a specific instant in time, reflecting the center of rotation for that particular movement.
When analyzing human movements, we estimate the position of the axis of rotation
