Unit 3 Flashcards
Define Vector Composition
Several force vectors added together (composed together) in order to get a single force vector (resultant force vector)
Define Vector Resolution
Taking one force vector and turning it into two components.
What is the significance of determining vector composition and vector resolution?
We can tell how much of the vectors are translations and rotations. If you know where the muscle is anatomically, and you know the axis, you can predict what will happen when that muscle contracts.
How does one simply add vectors that are collinear, coplanar forces to find the resultant force?
Collinear = parallel. The vectors can simply be added. (Force diagram from PHY 2)
How does one add vectors that are non-collinear, coplanar forces to find the resultant force?
You add the forces head-to-tail and find the resultant vector through the tail to head method.
What are the rectangle perpendicular (normal) and parallel (tangential) components of a force? (i.e. What does the perpendicular (normal) component represent and what does the parallel (tangential) component represent related to force of a muscle?
Perpendicular (normal) (rotational)–Perpendicular to the long axis of the normal bone. If it is the only component that moves, it will be rotational.
Parallel (tangential) (translational)–Parallel to the long axis of the moving bone. Some translational forces will compress and some will distract.
How does the parallel (tangential or translation) component of a resultant muscle force vector relate to compression and/or distraction of/at a joint?
The parallel component is dependent on where the rotational component positions the bone. The parallel component can then either pull the bone into the joint causing compression, or the parallel component can pull the bone away from the joint causing distraction.
How do the perpendicular and parallel components’ relationship to each other define how the joint works?
Some of the muscle action is stabilizing (compression) by the parallel component, while some of the muscle is rotating (torque) the arm in the perpendicular component.
Can you compare how torque is calculated using the perpendicular (rotational) component of a resultant force and its IMA versus the resultant force itself and its IMA? What do each of these calculations reveal?
Take the rotational component force and multiply by its long moment arm. It is equal to internal moment arm of the line of pull times line of pull of the muscle.
They are equal.
How does all this force analysis relate to external loads/forces?
The principles of force analysis for internal loads apply equally to external loads.
