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Lecture 8

# Kinesiology 2241A/B Lecture Notes - Lecture 8: Angular Velocity, Moment Of Inertia

Department
Kinesiology
Course Code
Kinesiology 2241A/B
Professor
Thomas Richard Jenkyn
Lecture
8

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Kin 2241b Introductory Biomechanics Keenan Vanderkooi
Assignment 4 250866706
1. If you are to collide with someone else who also possesses momentum,
conservation of linear impulse can be seen. When colliding, the added
momentum from both bodies remains the same as before the crash occurred,
however some of that momentum is distributed from one body to the other.
Therefore, if that person colliding with you weighed twice as much, you
would decelerate twice as much. The force that each of you received acted in
opposite directions, however due to the different weight distributions; you
would decelerate twice as much.
2. The mass of your arm is the amount of matter that it is made of, and the
resistance it has in respect to a change in linear motion. Newton’s first law
states that objects do not wish to be accelerated due to inertia, and the only
way to move it linearly is to apply a force that is proportional to the object’s
mass. This is different than the arm’s mass moment of inertia, which is the
resistance the object has in respect to a change in angular motion. Mass
moment of inertia is otherwise known as rotational inertia, and relates to
how much mass is away from the center of rotation. It is depicted as the
symbol I and is scalar. Mass moment of inertia can be changed through
body position, such as a figure skater releasing their hands from their sides
in order to slow down while rotating.
3. A) For a change in the radius of gyration to 1/3 k, the angular velocity would
increase 9 times.
B) For a change in the radius of gyration to 1/5 k, the angular velocity would
increase 25 times.
C) For a change in the radius of gyration to 6 k, the angular velocity would
decrease to 1/36 its original size.
D) For a change in the radius of gyration to 12 k, the angular velocity would
decrease to 1/144 its original size.
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