2. A person is standing still (not rotating) on a frictionless platform that can rotate. The moment of inertia of theperson-and-platform about its spin axis is 2.5 kg m².The person is holding a bicycle wheel with a radius of 25 centimeters. The mass of the wheel, 4.0 kilograms, isnearly all on its rim. The wheel has an angular velocity vector is 20 rad/sec up. The wheel is then flipped overso its angular velocity vector is now 20 rad/sec down. See the link in the class assignment page for a video ofthis experiment.a. What is the moment of inertia of the wheel about its axle? Almost all the mass is at the outer rim so we canapproximate this as a thin hoop.b. What is the magnitude and direction (up/down) of the initial angular momentum of the wheel?C. Assume that the angular speed of the wheel is unchanged when the wheel is flipped over, so that its finalangular velocity is 20 radians/second down, what is the final magnitude and direction (up/down) of theangular velocity of the person-and-platform?d. What is the minimum amount of work that the person must do during this process? (Hint: The change inkinetic energy is all from the person/platform since the rotational kinetic energy of the wheel does notchange) 1. A diver has a moment of inertia of 15 kg m² as she jumps off the diving board. She reduces her moment ofinertia to 5 kg m² when she tucks herself in during the dive. Her rotation rate is 6 rad/s after she tucks in.a. What is her angular momentum when she is in the tuck position? As always, start by writing the relationsyou will use in symbolic form first before substituting in numbers. Show numbers you use.b. The angular momentum of the system is conserved as long as there is no net external torque. Once thediver is the air, she will rotate about her center of mass. Neglecting air friction, the only external force inthis situation is gravity. Why is the torque due to gravity zero during the dive?C. What was her angular speed before she tucks in?d. How much work her muscles do in bringing herself into the tuck? This work converts chemical potentialenergy in her muscles into kinetic energy. Note that her tuck only affects the rotational motion, so you onlyneed to consider her rotational kinetic energy.Wmuscles = AEmech = Kf - K₁ =

Answered: Image /qna-images/answer/330de30c-31d3-47b3-b49e-c5f6e7533312.jpg

inertia to 5 kg m² when she tucks herself in during the dive. Her rotation rate is 6 rad/s after she tucks in. a. What is her angular momentum when she is in the tuck position? As always, start by writing the relations you will use in symbolic form first before substituting in numbers. Show numbers you use. b. The angular momentum of the system is conserved as long as there is no net external torque. Once the diver is the air, she will rotate about her center of mass. Neglecting air friction, the only external force in this situation is gravity. Why is the torque due to gravity zero during the dive? c. What was her angular speed before she tucks in? d. How much work her muscles do in bringing herself into the tuck? This work converts chemical potential energy in her muscles into kinetic energy. Note that her tuck only affects the rotational motion, so you only need to consider her rotational kinetic energy. Wmuscles = AEmech = Kf - K₁=

inertia to 5 kg m² when she tucks herself in during the dive. Her rotation rate is 6 rad/s after she tucks in. a. What is her angular momentum when she is in the tuck position? As always, start by writing the relations you will use in symbolic form first before substituting in numbers. Show numbers you use. b. The angular momentum of the system is conserved as long as there is no net external torque. Once the diver is the air, she will rotate about her center of mass. Neglecting air friction, the only external force in this situation is gravity. Why is the torque due to gravity zero during the dive? c. What was her angular speed before she tucks in? d. How much work her muscles do in bringing herself into the tuck? This work converts chemical potential energy in her muscles into kinetic energy. Note that her tuck only affects the rotational motion, so you only need to consider her rotational kinetic energy. Wmuscles = AEmech = Kf - K₁=

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter1: Units, Trigonometry. And Vectors

Section: Chapter Questions

Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...

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Concept explainers

Torque

Torque is the rotational equivalent of linear force in physics and mechanics. Based on the course of study, it is also known as the moment of force, rotational force, or turning effect.

Question

2. A person is standing still (not rotating) on a frictionless platform that can rotate. The moment of inertia of the
person-and-platform about its spin axis is 2.5 kg m².
The person is holding a bicycle wheel with a radius of 25 centimeters. The mass of the wheel, 4.0 kilograms, is
nearly all on its rim. The wheel has an angular velocity vector is 20 rad/sec up. The wheel is then flipped over
so its angular velocity vector is now 20 rad/sec down. See the link in the class assignment page for a video of
this experiment.
a. What is the moment of inertia of the wheel about its axle? Almost all the mass is at the outer rim so we can
approximate this as a thin hoop.
b. What is the magnitude and direction (up/down) of the initial angular momentum of the wheel?
C. Assume that the angular speed of the wheel is unchanged when the wheel is flipped over, so that its final
angular velocity is 20 radians/second down, what is the final magnitude and direction (up/down) of the
angular velocity of the person-and-platform?
d. What is the minimum amount of work that the person must do during this process? (Hint: The change in
kinetic energy is all from the person/platform since the rotational kinetic energy of the wheel does not
change)

1. A diver has a moment of inertia of 15 kg m² as she jumps off the diving board. She reduces her moment of
inertia to 5 kg m² when she tucks herself in during the dive. Her rotation rate is 6 rad/s after she tucks in.
a. What is her angular momentum when she is in the tuck position? As always, start by writing the relations
you will use in symbolic form first before substituting in numbers. Show numbers you use.
b. The angular momentum of the system is conserved as long as there is no net external torque. Once the
diver is the air, she will rotate about her center of mass. Neglecting air friction, the only external force in
this situation is gravity. Why is the torque due to gravity zero during the dive?
C. What was her angular speed before she tucks in?
d. How much work her muscles do in bringing herself into the tuck? This work converts chemical potential
energy in her muscles into kinetic energy. Note that her tuck only affects the rotational motion, so you only
need to consider her rotational kinetic energy.
Wmuscles = AEmech = Kf - K₁ =

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