Kinetics
Aspects of force
1. magnitude
2. direction
3. point of application
what is a torque
a turning effect of some force
what is CoG
a point within a body or segment about which that body or segment would balance without tendency to rotate
two types of mechanical energy
kinetic and potential
what is momentum
a quantity of motion that is produced by an increase or decrease in mass or velocity
What are linear, concurrent, and parallel forces?
Linear: forces applied in the same direction and same line of action
concurrent: forces applied at the same point but different angle
parallel: forces applied at different directions and different line of action
how can a torque be modified
changing the length and the magnitude of the force
forces that affect stability
size and shape of the base
height of the object
line of gravity to the base
what is a moment arm
The perpendicular distance from the line of action to the pivot point, axis, or center of mass
what is friction and what is is responsible for
forces that modify motion
1. weight
2. fluid forces
3. contact forces
what are levers and how many classes are there/what are they?
rigid bars that rotate about a fixed point to overcome a resistance when a force is applied
3 classes
(ARE)
Location of CoG is dependent upon
anatomical position
standing position
external forces
what is the product of a torque
Product of the force magnitude and the perpendicular distance from the line of force to the axis of rotation
calculation of muscle torques (3)
the size of the muscle force
angle at which the muscle pulls
perpendicular distance from the muscle to the joint
muscles can have two simultaneous functions, what are they
movement and stablizing
what is moment of inertia
The size of the angular inertia is dependent on the quantity of rotating mass and the distribution of that mass around the axis of rotation
All things equal lowering the CoG will..
greater the bodies stability
If you increase time what will happen to force
decrease
what two forces influence friction
normal reaction forces and frictional forces
difference between positive and negative work
positive: concentric contraction, performed in the same direction as the body moves
negative: eccentric contraction, performed in the opposite direction as body moves
describe all three class levers
1st: axis of rotation is in the middle, Most versatile lever because it can be used for any type of mechanical advantage
2nd: resistance force is in the middle, Force advantage usually exists for effort force
3rd: effort is in the middle, most musculoskeletal arrangements, advantage in ROM/speed but not force
sum of all forces and torques on the body must equal
0
what is impulse
the product of force and time which will affect mass and velocity
Newtons Angular Laws
1. a rotating body will continue to turn about its fixed point with constant angular momentum unless an eccentric force is exerted
2. the rate of change of angular momentum of a body is proportional to the torque causing it and direction changes in which the torque acts
3. for every torque that is exerted by one body on another there is an equal and opposing torques exerted by the second body on the first