Kinesiology 2241A/B Lecture 4: Biomechanics Assignment 4
Course CodeKinesiology 2241A/B
ProfessorThomas Richard Jenkyn
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1. If you were to collide with another person who weighed twice as much as you, you would
decelerate twice as much as the heavier person. This is because since each of you received the
same force (but in opposite directions) , but your mass is half of the heavier individuals, the
acceleration would be twice as large since there is less inertia to overcome. (ie. a = F/m).
2. The mass inertia of your arm is its resistance to a change in linear motion, which is measured
using the mass of your arm. In contrast, the arm’s mass moment of inertia is its resistance to a
change in its state of angular motion, which is measured by its mass as well as how far away the
mass is distributed from its axis of rotation.
3. Impacts on angular velocity based off of changes in the radius of gyration:
1. 1/3 k: a reduction of the radius of gyration to 1/3 of its original magnitude would cause
the angular velocity to increase by 9 times.
2. 1/5 k: a reduction of the radius of gyration to 1/5 of its original magnitude would cause
the angular velocity to increase by 25 times.
3. 6 k: an increase of the radius of gyration by 6 times would cause the angular velocity to
decrease to 1/36 of its original magnitude
4. 12 k: an increase of the radius of gyration by 12 times would cause the angular velocity
to decrease to 1/144 of its original magnitude.
4. Draw arbitrary trajectories for the following situations:
a. Two projectiles, with take-off velocities that are equal in magnitude and at a 35° angle.
one takes off from 1.5m and the other from 2m. Both land on the ground level.
b. Two projectiles with take-off heights that are equal and at a 35° angle but with take-off
speeds of 20 m/s and 25 m/s. Both land at the same level.
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