ANgular kinetics Flashcards
What is angualr kinetics?
causes of angular motion
WHat is angular (rotary inertia). QUnatified as?
– property of an object to resist changes in its angular motion.
- moment of inertia (I)
is moment of inertia scalar or vector?
scalar
what is SI unit for moment of inertia
kg x m^2
What is the ri in the moment of inertia equation
radius frolm particle i to axis of rotation a
what is the radius of gyration?
the distance from the axis of rotation to the point at which an objects mass could be concentrated without changing angular inertia of an object
What is the differnencce between linear and angular inertia
linear inertia is dependent only on mass while angular is dependent on mass and distribution of mass (r or k)
What is Ka? What is r? in angular inertia
ka is radius of gyration about axis a
r is radius (distance) from particle i to axis of rotation ‘a’
An object free to rotate will rotate about what?
Its CG
what is an eccentric axis/when does it occur
Not thru an objects CG, occurs in objects that we swing as they have an axis of rotation thrust upon them
Why can objects have multiple moments of Inertia?
becuase they can rotate abtout many diffenect axes
What is angular inertia dependent on?
mass and distribution of mass (r or k)
Whats greater the moment of inertia about axis b or about the centre of gravity?
axis b
What are the 3 different axes which it is possible to have moments of inertia?
anteroposterior (saggital), longitudianl (vertical), transverse (frontal)
How many moments of inertia can each axes have?
1
Can the moment of our body change the moment of inertia, why?
yes it can because our body is not rigid and the cg changes
linear velocity ____ as distance from axis of rotation increases
increases
as implement length increases moment of intertia ____ which makes it _____ to accelarate the object to achieve the same angular velocity
also increasess so it makes it harder to accelrate
What is H
angular momentum
What does angular momentum quantify?
the angular motion of an object
is angular momentum scalar or vector?
vector?
what is the si unitu for angular momentum?
kgxm/s^2
For rigid objects what is angular momentum dependeont on?
What about for non-rigid objects?
for rigid objects it depns only on w (angular velocity) not moment of inertia bc it remains constant
For non-rigid it depends on both moemnt of inertia and angular velocity
Do distribution of mass and mass have the same effect on linear inertia?
no. distirbution of mass can change and has a greater effect than the mass on linear inertia
In a symmetrical acitvity what is the total angular moemntum of the body?
0 - equal and opposture for left/roght arms and legs 0 momentun for trunk bc its not rotating
How dose angular momentum relate to newtons first law?
angular momentum of an object remains constant
unless a net external torque acts on it
for a rigid body where I is constant the angukar velocity must also be constant
For a non-rigid body, it isn’t necessary for
angular velocity to be constant – only that I × ω
remains constant if no external torques ac
what is net torque according to coservation of angukar momentum?
0
How does angular momentum relate to newtons second law
Change in angular momentum of an object is
proportional to net external torque acting on it and in the direction of the torque
Angular accelation will be ____ porportonal to torque and _____ porpotional to its moemtn of inertia
directly, indierectly
according to law of acceleratio, net external torque exerted on an object is ____ to the rate of change on angular momentum
porportional
What are three ways that changes in angular momentum may be seen as
- speeding up or slowing down of angular velcoty
change in direction of the axis of rotation
change in the moment of inertia
what is angular impulse
change in angular momentum over time
torque application can be prolonged by starting with a ____ moment of inertia and ____ to increase ___
stary w large moment of inerta and decrease it to increase angular velocity
How does angular momentum relate to Newtons 3rd law
for every torque eexerted on an object exerts an equal and opposite torque on the first object
