LECTURE #19 - angular kinetics (2) Flashcards
what does angular motion refer to ?
rotation about a point
when does angular motion occur ?
when a force acts about a distance from a fixed point
what does angular kinetics refer to ?
the branch of mechanics that deals with the causes of angular motion
what is inertia ?
the property of an object that resists change in motion
what is linear inertia quantified as ?
an objects mass
what is angular inertia ?
the property of an object to resist changes in its angular motion
what is mass ?
measure of object’s inertia or resistance to change in acceleration
what is moment of inertia = ?
object’s resistance to a change in a angular acceleration
moment of inertia depends on what two factors ?
mass and distribution of mass relative to axis of rotation
TRUE OR FALSE
in the human body masses cannot be concentrated into single points (non-symmetrical body parts)
TRUE
what is radius of gyration (k) ?
the distance that represents how far away from the axis of rotation a body’s mass is distributed
COM vs. Radius of Gyration ; what is centre of mass ?
point where gravitational force is applied (the balance point)
COM vs. Radius of Gyration ; what is radius of gyration ?
- distance mass is distributed from a specific axis of rotation
- point where mass can conceptually be concentrated such that it does not alter the moment of inertia (I)
TRUE OR FALSE
rotation can not occur about different axes
FALSE
rotation can occur about different axes
TRUE OR FALSE
each axis has its own moment of inertia
TRUE
TRUE OR FALSE
each axis shares the same moment of inertia
FALSE
each axis has ITS OWN moment of inertia
FILL IN THE BLANK
the _______ mass is distributed to the axis of rotation, __________ it is to rotate
the CLOSER mass is distributed to the axis of rotation, EASIER it is to rotate
how many principal axes does the human motion occur about ?
3
what are the three axes for human motion ?
- transverse
- frontal
- longitudinal
linear momentum is the product of what ?
mass and velocity
for the formula M = mv, what does M quantify ?
the linear motion of an object
what is angular momentum the angular analog of ?
angular momentum is the angular analog of linear momentum
what is angular momentum a product of ?
body’s rotational inertia and rotational velocity about an axis
TRUE OR FALSE
angular momentum is a vector quantity
TRUE
TRUE OR FALSE
direction is same as the angular velocity it defines ?
TRUE
does angular momentum have magnitude and direction ?
YES
what is the conservation of angular momentum ?
declares that the angular momentum of an isolated system will remain the same regardless of any movements or torques that are produced internal to the system. as long as no external toque is applied to the system
what is newtons first law ?
law of inertia
define the law of inertia :
any given system will continue to move with constant momentum unless an external force acts to change that momentum
what is newtons second law ?
law of acceleration
define the law of acceleration :
- the change in angular momentum of an object is proportional to the net external torque exerted on it , and this change is in the direction of the net external torque
- the net external torque is proportional to the rate of change in angular momentum the change in
what is newtons third law ?
angular analog / law of reaction
define angular analog / law of reaction :
for every torque exerted by one body on another body, there is an equal and opposite torque e exerted by the second body on the first
TRUE OR FALSE
torque generated by one body part to rotate that part results in a counter-torque by another body part (opposite direction)
TRUE
