Question

A physics student is sitting on a rotating platform. He is holding a heavy weight in each of his outstretched hands. At request of his physics instructor(!) he carries out various manoeuvres to try to change his angular velocity. Which of the following scenarios are described correctly? Select True or False. 1) True False Starting at rest, he drops the weights. His angular velocity decreases. 2) Starting with angular velocity ωgw, he brings the weights in to his chest. His angular velocity reverses. 3) Starting at rest, he brings the weights in to his chest. His angular velocity increases 4) Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. He then stretches his other hand back out to its original position. His angular velocity (after the manouvre is complete) has decreased. 5) Starting at rest, he brings the weights in to his chest. His angular velocity decreases. 6) Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. His angular velocity (after the manoeuvre is complete) has reversed. 7) Starting with angular velocity ωgw, he brings the weights in to his chest. His angular velocity increases. 8) Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. He then stretches his other hand back out to its original position. His angular velocity (after the manouvre is complete) has increased. 9) Starting with angular velocity ωgw, he raises his feet, and points them outwards from the chair as far as he can. His angular velocity increases. 10) Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. He then stretches his other hand back out to its original position. His angular velocity (after the manouvre is complete) has not changed.

Answer 1

Which of the following scenarios are described correctly?       Select - True or False

1. Starting at rest, he drops the weights. His angular velocity decreases.     (FALSE)

2. Starting with angular velocity ωgw, he brings the weights in to his chest. His angular velocity reverses.   (FALSE)

3. Starting at rest, he brings the weights in to his chest. His angular velocity increases.   (FALSE)

4. Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. He then stretches his other hand back out to its original position. His angular velocity has decreased.        (FALSE)

5. Starting at rest, he brings the weights in to his chest. His angular velocity decreases.      (FALSE)

6. Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. His angular velocity has reversed.       (TRUE)

7. Starting with angular velocity ωgw, he brings the weights in to his chest. His angular velocity increases. (TRUE)

8. Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. He then stretches his other hand back out to its original position. His angular velocity has increased.      (TRUE)

9. Starting with angular velocity ωgw, he raises his feet, and points them outwards from the chair as far as he can. His angular velocity increases.       (TRUE)

10. Starting with angular velocity ωgw, he transfers both the weights to one outstretched hand. He then stretches his other hand back out to its original position. His angular velocity has not changed.   (TRUE)