final exam Flashcards
coplanar
any system of forces acting in a single plane
Concurrent
any system of forces acting at a single point
inertia
resistance to motion, directly related to the mass of the object
impact peak
impact on the body in landing
Joint reaction force
net force acting across the joint
friction
a force that acts parellel to the interface of two surfaces
centripetal force
act toward the center of rotation when an object moves along a curved path
pressure
used to describe force distribution
center of pressure
a displacement measure indicating the path of the resultant GRF vector on the force platform
passive peak
a phase that is not considered to be under muscular control and is influenced by impact velocity
active peak
second peak in GRF, role of muscles play in the force development
Law of inertia
every body continues in its state of rest until it is acted upon by an external force
Law of acceleration
the rate of change of momentum of a body is proportional to the force causing it, and the change takes place in the direction of the force
Law of action-reaction
for every action there is an equal and opposite reaction
Torque (Moment of Force)
a force that causes a rotation, the product of a force and the perpendicular distance to its line of action
Torque arm (Moment Arm)
The distance r is referred to as the
eccentric force
when the force is not applied through the pivot point. literally an off center force
force couple
two torques that produce a rotation about their longitudinal axis (backward force with one foot and a forward force with the other foot) F*D=force couple
Moment of inertia
dependent not only on the mass of the object but also on the distribution of mass with respect to an axis of rotation
Radius of Gyration
denotes the segments mass distribution about the axis of rotation and is the distance from the axis of rotation to a point at which the mass can be assumed to be concentrated without changing the inertial characteristics
Parallel Axis Theorem
the moment of inertia can be calculated about any parallel axis, given the moment of inertia about one axis, the mass of the segment, and the perpendicular distance between the parallel axis.
Angular momentum
is the quantity of angular motion of an object and has units of Kg-m2.s-1
Angular impulse
T x dt
conservation of angular momentum
when gravity is the only external force acting on an object, as in projectile motion, the angular momentum generated at takeoff remains constant for the duration of the flight
local angular momentum
the angular momentum of a segment about its own center of mass is referred to as
remote angular momentum
the angular momentum of a segment about total body center of mass is referred to as
center of gravity
the body weight vector originates at a point referred to as
center of mass
the point about which the body’s mass is evenly distributed
segmental method
involves knowledge of the masses and the location of the centers of mass of each of the body’s segments
lever
a rigid rod that is rotated about a fixed point or axis called the fulcrum
a lever consists of
a resistance force, an effort force, a barlike structure, and a fulcrum
two moment or lever arms are designated as
the effort arm and the resistance arm
