Levers Flashcards
what are the lever forces in the body?
lever = bone/segment axis = joint weight = body part/ segment or applied resistance force = muscle
when does the force balance the weight/resistance?
when the product of FORCE (X) the LENGTH of the force arm = product of the weight/resistance (X) LENGTH of the resistance arm
where is the weight/resistance arm?
distance btwn axis & applied force
where is the force arm?
distance btwn axis & resistance
what is the purpose of the lever?
to gain mechanical advantage
what equation describes all classes of levers?
F X FA = R X RA
each side of equation represents TORQUE
what is the purpose of a 1st class lever?
seesaw
to gain either force or distance but usually sacrifice force for speed
what is the purpose of a 2nd class lever?
resistance between force and axis
speed is sacrificed for power
what is the purpose of a 3rd class lever?
power sacrificed for speed
most common in human body b/c permits muscles (F) to be inserted near the joint to produce distance + speed of motion
what is torque?
measure of a forces tendency to produce a rotation about an axis (how hard something is rotated)
like a twist
what is the mathematical equation for torque?
T = F (X) Perpendicular Distance
what is a force couple?
2 forces of equal magnitude acting at a distance from each other and in opposite directions, causing roatation
what is a moment arm?
perpendicular distance from the point of application of a force to the axis of rotation (lever arm)
what is body mechanics used for?
to keep spine in safe & aligned position
what does vector quantity represent?
both magnitude and direction
