Final answer:
In figure skating, athletes use the conservation of angular momentum to execute spins, pulling in their limbs to spin faster, and experience minimal net torque due to the low friction of ice. Their body positions in jumps and spins are integral to manipulating their moment of inertia and controlling their movements according to physics principles.
Step-by-step explanation:
Physics of Jumps and Spins in Figure Skating
In figure skating, athletes perform various jumps and spins that are not only aesthetically impressive but also demonstrate key principles of physics. One of the fundamental concepts in play is the conservation of angular momentum, which a figure skater utilizes effectively during a spin. When a skater pulls their arms and extended leg towards their body, as depicted in Figure 10.2, they reduce their moment of inertia. According to the conservation of angular momentum when the moment of inertia decreases, the skater’s rotational velocity must increase to compensate, resulting in a faster spin.
The net torque on a spinning figure skater is almost zero due to the low friction between the skates and the ice. The force (F) applied by the friction is minimal and acts very close to the spin's pivot point, the point over which the body is rotating, which has a small lever arm (r), leading to an extremely small torque. As a consequence, the effect of friction on the rate of the spin is negligible, allowing the skater to maintain the spin without excessive loss of speed.
The striking poses skaters hold during jumps and spins are more than just for show. For example, in Figure 10.39, twin skaters can be seen approaching each other at identical speeds and then grabbing each other’s hands to spin together, an act that further demonstrates the principles of momentum and torque. Changes in body position while in the air during jumps also utilize physics to control the skater’s rotation and landing position.