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Lecture 4

# Kinesiology 2241A/B Lecture Notes - Lecture 4: Angular VelocityExam

Department
Kinesiology
Course Code
Kinesiology 2241A/B
Professor
Dr Jim Dickey
Lecture
4

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Assignment 4: Biomechanics
Christian Megan Turres
250911289
1. If a collision occurred with someone who weighed twice as much as your relative magnitude
would decelerate twice as much. The magnitude of acceleration is affected by mass, because
the person colliding into you weighs twice as much, you would both experience an opposing
force but their force would have a greater impact. Thus, making you decelerate twice as much
than the person that weighs more.
2. The mass of your arm is what makes up the arm and its inertia. Inertia as Newton’s first
law dictates is that objects don’t like to be accelerated due to inertia they possess. The
mass of your arm is related to inertia as is acts to prevent linear acceleration. Mass
moment of inertia differs from mass of your arm as it shows resistance against being
angularly accelerated. Angularly accelerated is also known as rotational inertia.
Rotational Inertia can be determined by first calculating the Inertia which is mass times
how far away the mass is from the center of axis/ radius squared. The farther the mass
from the center of rotation the bigger the rotation, the closer the mass the faster the
angular velocity. An example of this would be when a ballerina spins on her toe. First
the ballerina starts with her arms out to create a Rotational inertia and then pulls them
in to spin quicker which increases the angular velocity.
3.
a) If the radius gyration changed to 1/3 k the angular velocity would increase by 9 times
b) If the radius gyration change to 1/5 k the angular velocity would increase by 25 times
c) If the radius gyration change to 6k the angular velocity would decrease to 1/36 of the
initial size
d) If the radius gyration change to 12k the angular velocity would decrease to 1/144 of the
initial size.
4.