As you can see in the video, the figure skater spins slower
while her arms and leg are extended out, and gains speed as she pulls her limbs
in closer to her torso. What causes this change?
Rotational inertia allows an object to resist changes in
spinning or circular motion. The factor that affects rotational inertia is not
the AMOUNT of mass of the object, but rather the DISTRIBUTION of mass and its
location on the object.
That being said, when mass is closer to the axis of rotation
the object will have a smaller rotational inertia (easier to move). And when
mass is further from the axis of rotation, the object will have a larger
inertia (harder to move).
In terms of the ice skater…
While her arms are extended out, her mass is further from
the axis of rotation, thus yielding a larger inertia. With the larger
rotational inertia, she will move slower. As she brings her arms and leg
towards her body, she is bringing her mass closer to the axis of rotation,
resulting in a smaller rotational inertia. Hence, she spins faster.
Hello! Great video and analysis Stafford. I liked the video because it related to a real life application that I could easily use on a problem in future assessments. I liked the analysis because it was really organized and straight forward. I don't see anything else that could of been added to this resource. I hope future post are as concise and interesting as this one.
ReplyDelete