L21;C14 Flashcards
We treat the body as as ______ ______ _____ while dealing with angular kinetics
One rigid object
We must look at ______ and ______ in order to settle equilibrium
Forces, torques
First law of inertia (Newton’s) with respect to angular kinetics
Objects will remain in current states unless acted upon by external torques. ΣT=0
Explain the second law of acceleration for angular kinetics
An applied net torque causes an object to accelerate directly proportional to the torque magnitude in the same direction of force.
ΣT=Ia
Explain the third late of reaction in angular kinetics.
Every applied torque has an equal or opposite reaction torque.
T action= T reaction
______ forces, which can be considered off centre, may cause rotation and translation
Eccentric
____ forces can only produce translation
Centric
True or false: individual forces may have potential to produce rotation
True
____ is a measure of inertia of an object
Mass
Heavier object, means _______ to change state of motion
Harder
In angular terms, heavier an object means harder to ______ ______ which evidently determines how mass is distributed in an object
Change motion
In linear kinetics: inertia is directly proportional to _____ _____
In angular kinetics: inertia is directly proportional to ______ AND _________
objects mass
Mass, distribution
What is angular inertia?
The mass moment inertia is the inertial property for angular motion and is calculated by summing particles masses and distance to axis of rotation
What is the formula for the mass moment of inertia?
I=mk^2
In most objects, what happens to mass? Does it differ with respect to its mass moment of inertia?
In most objects, mass doesn’t change. But MMI will change depending on AoR
What is k? What does it represent?
K represents the radius of gyration, this is used to represent an objects mass distribution with respect to given object
When is K smallest?
When rotating around its own axis
How can changing the shape influence the mass?
Changing the shape influences how mass is distributed around an axis of rotation
What are the three axi of rotation?
Anteroposterior, medilateral, longitudinal
Momenta are _______ that possess both ______ and _______
Vectors, magnitude, direction
Angular momentum of single segments with respect to AoR consists of TWO main components:
- Local term- segments angular momentum about its own CG
2. Remote term- segments angular momentum about whole body CG
During a whole body action such as a dive, momentum is conserved meaning I and w change. How and why do they?
As you tuck in from the dive, your ‘I’ begins to decrease due to the K value decreasing. K value decrease due to the CoM coming closer to the AoR on the body.
What is the formula for angular impulse? What can you derive it to?
T•∆t= F•dt•∆t
Is angular impulse a vector or scaler?
It is a vector since its magnitude and direction are specified
Another world for radial acceleration is _________ accerlation
Centripetal
What does centripetal acceleration result from?
A change in direction of the transverse component of the point of velocity
Since a point is accelerating towards the centre, what kind of force must be involved?
A centre seeking force
Any force that causes an object to exhibit circular motion is referred to as _______ ________
Centripetal force
Explain the concept of inertia again with respect to kinetics? (Use accerlation in answer)
It is the tendency to resist acceleration, a bodies inertia is directly proportional to its mass
More mass closer to axis of rotation ________ to rotate the object
Easier
What are the three factors that effect the magnitude of the bodies of angular momentum?
- Mass
- Distribution of mass
- Angular velocity
What has the greatest effect on angular momentum?
Distribution of mass
What happens to angular momentum in the absence of torques?
It is constant
What is the most influential factor for rotation?
Speed
