Lecture #2 (Forces & Tissue Properties) Flashcards
What is the definition of force?
That which pushes or pulls through direct mechanical contact or through the force of gravity to alter the motion of an object.
What are internal forces?
Forces that act on various structures of the body (i.e. muscle forces)
What are external forces?
Forces that are outside the body (i.e. weight, gravity, air/water resistance, friction, other objects, etc.)
What type of quantity is force?
A vector
What does a vector force have? (3)
Magnitude
Direction
Point of application
True or false:
Gravity has a point of application.
False–gravity is a constant force, therefore it does not have a point of application.
What type of movement has no effort on the part of the subject involved, and the motion is completely due to an outside force?
Passive
What type of movement is produced by the subject’s own muscular activity?
Active
How it the human body designed to move? Why?
The human body is made for bursts of movement and sustained momentum rather than slow movements. This is because it takes less energy for us to do so.
What is the imaginary point representing the weight center of an object?
Center of gravity (COG)
Where is our COG?
Anterior to S2
True or false:
Males have a slightly lower center of gravity than women.
False
What is the imaginary vertical line that passes through the center of gravity (the action line and direction of force of gravity on a person)?
Line of gravity (LOG)
When does a person fall over?
When their line of gravity gets outside the base
What type of forces cause movement?
Unbalanced forces (if the forces were balanced, then no movement would happen because of a net force of 0)
What type of force occurs within the body? Outside the body?
Internal; external
What type of force is produced by muscular activity?
Internal
What is an example of a constant, external force?
Gravity
What is the magnitude of a force?
The amount of force being applied (the power behind the force)
What is weight? (formula)
Mass x acceleration due to gravity
True or false:
Muscles can create various magnitudes of force to create, halt, and control motion.
True (this is why kids can be uncoordinated)
How does force occur in the body?
In direct proportion to the number and size of fibers contracting in the muscle (typically measured in groups of muscles)
How do forces work in the body?
They go through a lever system (skeletal system)
How do you want your base of support?
As wide a possible
What is the point of application?
The point at which a force is applied to an object
Where does gravity have its point of application? For a muscle?
COG; the muscle’s attachment to a bony lever (point of intersection of the line of force and the mechanical axis of the bone)