Kinesiology 3341A/B Lecture Notes - Lecture 9: Angular Momentum, Ground Reaction Force, Sagittal Plane

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13 Dec 2019

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If you are in a conservative system, the amount of energy that you have is constant, and therefore your angular momentum is constant. Law of conservation of momentum: the total (linear/angular) momentum of a system remains constant unless external forces/moments in uence the system. If you apply a moment, it will change angular momentum in the air, you conserve angular momentum (unless something applies a moment and changes it) Angular momentum (h)= moment of inertia (i) x angular velocity (w) Because angular momentum remains constant in the air, angular velocity and moment of inertia must change in order to maintain it. 5= 99kgm^2/s: radius decreases dramatically, therefore having a large impact on moment of inertia (i= mr^2) remote terms, angular velocity= 99/11= 9m/s. If you are airborne, angular momentum is conserved unless a moment is applied you will rotate, but you can manipulate how fast you rotate. Cats are able to exchange angular momentum between the segments of the body.

Related Questions

Goal Apply conservation of angular momentum to a simplesystem.

Problem A student sits on a pivoted stool while holding a pair ofweights. (See Figure) The stool is free to rotate about a verticalaxis with negligible friction. The moment of inertia of student,weights, and stool is 2.25 kg Â· m2. The student is set in rotationwith arms outstretched, making one complete turn every 1.26 s, armsoutstretched.

Question If the student suddenly releases the weights, how does hisown angular momentum, rotational kinetic energy, and angular speedchange? (Select all that apply.)

His rotational angular speed decreases.
His rotational angular speed remains the same.
His angular momentum remains the same.
His rotational kinetic energy remains the same.
His angular momentum increases.
His angular momentum decreases.
His rotational angular speed increases.
His rotational kinetic energy increases.
His rotational kinetic energy decreases.

A star with an initial radius of 1.00 108 m and period of 30.0 dayscollapses suddenly to a radius of 1.00 104 m.

(a) Find the period of rotation after collapse.

(b) Find the work done by gravity during the collapse if the massof the star is 2.00 1030 kg.

The only force doing work on the system is gravitation, so the workdone by gravitation is the change in kinetic energy of the star.J

(c) What is the speed of an indestructible person standing on theequator of the collapsed star? (Neglect any relativistic or thermaleffects, and assume the star is spherical before and after itcollapses).

HINTS
* Do you expect the initial angular speed to be larger or smallerthan the final angular speed? How is angular speed related toperiod of rotation?

* Is the initial moment of inertia larger or smaller than the finalmoment of inertia?

* Is angular momentum conserved?

* As the star collapses, do you expect the period of rotation tobecome smaller or larger?

Kinesiology 3341A/B Lecture Notes - Lecture 9: Angular Momentum, Ground Reaction Force, Sagittal Plane

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