In figure skating, a triple Axel is a jump in which the figure skater leaps into
ID: 1262959 • Letter: I
Question
In figure skating, a triple Axel is a jump in which the figure skater leaps into the air while facing forward, performs 3.5 revolutions, and then lands facing backwards. During the spin, the skater hugs his/her arms close to the body. Choose the answer that best explains WHY the figure skater does this. Think about the experiment you performed on the rotating stool. Select one: a. Due to conservation of energy, pulling the arms close to the chest increases the figure skaters potential energy and thermal energy, allowing him/her to jump higher (which gives the figure skater more time to perform the triple Axel) and retain more body heat for future maneuvers. b. Due to the conservation of frictional forces, figure skaters pull their arms into their chests to decrease the effects of friction. Decreasing the effects of friction during the spin helps the figure skater spin faster to fully complete the triple Axel. c. Due to the conservation of stable forces, the figure skater?s arms naturally get pulled inward. It is impossible for the figure skater to force his/her arms outward. d. Due to conservation of angular momentum, decreasing the effective radius of the figure skater by pulling in the arms increases the angular velocity of the figure skater. This allows the figure skater to spin faster in the air to fully complete the triple Axel. You are swinging a yo-yo around in a circle above your head. Assume this is a perfect system: the mass of the string is negligible, the yo-yo is a point mass and your arm is a perfectly vertical axis of rotation. Given the mass of the yo-yo is m and the length of the string (radius of the circle traced by the yo-yo) is L, you find the moment of inertia to be I. If you double the length of the string, what is the new moment of inertia? Hint: Consider the equation for moment of inertia of a point mass about an axis in your lab manual. Select one: Imagine you have a system of two buckets as shown below. The buckets are spinning about an axle with frictionless bearings at some angular velocity, Ohm. It starts to rain. What happens to the two-bucket system? Think about angular momentum. Select one: a. Ohm must decrease to conserve angular momentum because because the rain increases me mass of the system (which increases the moment of inertia). b. Ohm must increase to conserve angular momentum because because the rain increases the mass of the system (which increases the moment of inertia). c. Ohm remains constant to conserve angular momentum because the amount of rain falling into one bucket equals the amount of rain falling into the other bucket. Any changes due to the rain therefore cancel. d. Ohm remains constant to conserve angular momentum because the rains kinetic energy is in the downward direction and does not affect the momentum of the buckets, which is in the horizontal plane.Explanation / Answer
1. OPTION A. Mass increases, moment of inertia increases, thus, w must decrease by conservation of angular momentum.
2. OPTION D. It decreases the effective radius.
3. OPTION B. I varies directly as the square of the radius. Thus, as r is multiplied by 2, I is multiplied by 2^2 = 4.