Angular Kinetics 2 Flashcards
What is the 1st Law: the law of inertia
A body willl maintain a constant state of rest or constant velocity or state of angular motion unless acted on by an external force/torque
IN linear kinetics, inertia is quantified by…
the mass of the object - resistance to a change in the state of motion
Angular inertia is
the property of an object to resist changes in its angular motion
Angular inertia is affected by…
- The mass of an object
- The distribution of mass of an object relative to the axis of rotation
___ quantifies angular inertia
Moment of inertia
The greater the distance that particles are located away from the axis of rotation the…
harder it is to rotate
What is the equation for moment of inertia
I = sum of mass x radius ^s
What is the radius of gyration
radial distance where all the mass can be located and have the same resistance to rotation
What does moment of inertia have to do with human movement
Understanding the moment of inertia of limb segments and even the whole body can be useful when considering the resistance of a human (limb segment) or whole body to rotate
Resistance to rotate is dependent on an object’s
moment of inertia
Moment of inertia is related to…
The mass and distribution of mass
Where does the smallest moment of inertia occur?
at the centre of gravity
Human and animals can alter the position of the CoG and have variable….
moments of inertia
A moment of inertia can exist for each…
axis
A sprinter reduces the moment of inertia about the hip by….
flexing the knee
A sprinter flexes her leg at the knee when she accelerates her leg during the swing through, this….
reduces the moment of inertia about the hip joint (axis of rotation)
Performance of a sprinter is improved by….
moving body segments closer to the axis of rotation
angular momentum is..
the tendency for an object to remain in angular motion
What is angular momentum determined by
The moment of inertia of an object and its angular velocity
Because the human body is a non-rigid object a person can alter their
moment of inertia and thus change their angular velocity while maintaining the same angular momentum
When spinning what does extending arms mean?
a larger moment of inertia and a smaller angular velocity
when spinning what does bringing arms in do
a smaller moment of inertia and a greater angular velocity
Think of a diver doing a back flip, when is moment of inertia the lowest
At peak when in tuck position
What is the Angular Law of Acceleration
A torque applied to a body causes an angular acceleration of that body of a magnitude proportional to the torque, in the direction of the torque, and inversely proportional to the moment of inertia
The greater the inertia of an object, the …
more force (torque) is required to make it accelerate
If a net external torque is exerted on an object at a distance from the axis of rotation, the object will accelerate angularly in the direction of the net external torque, and its angular acceleration will be
proportional to the net external torque and inversely proportional to its moment of inertia
What is angular impulse
a measure of a torque applied
The net torque acting over some interval of time will cause
a change in angular momentum of an object
Changes in the momentum of a system depend on:
- The magnitude of external torques
2. The time over which the torques act
What is the SI units for momentum
N.m.s
