In a skating jump, a skater rotates around their vertical central axis. During the jump, the skater's rotation rate is increased by bringing their arms into their side. a) When bringing their arms into their side, do es the rotational kinetic energy of the skater go up, go down or stay the same? If it changes, where do es the energy for this change come from or go to? b) Show that the change in rotational kinetic energy of the skater ∆KR can b e found by (see image) here KRi is the initial rotational kinetic energy of the skater, ωf is the nal angular sp eed and ωi is the initial angular speed. c) During the jump, when the skater draws their outstretched arms inwards, what total torque is acting on the skater if their final rate of rotation is two rotations p er second?
In a skating jump, a skater rotates around their vertical central axis. During
the jump, the skater's rotation rate is increased by bringing their arms into
their side.
a) When bringing their arms into their side, do es the rotational kinetic energy
of the skater go up, go down or stay the same? If it changes, where do es the
energy for this change come from or go to?
b) Show that the change in rotational kinetic energy of the skater ∆KR can
b e found by (see image) here KRi is the initial rotational kinetic energy of the skater, ωf is the nal
angular sp eed and ωi is the initial angular speed.
c) During the jump, when the skater draws their outstretched arms inwards,
what total torque is acting on the skater if their final rate of rotation is two
rotations p er second?
d) After landing again, the skater is able to stop rotating and come to a
complete standstill in 0.7s. What is the average ratio of the torque on the
skater to the skater's total moment of inertia during the time they come to a
standstill?
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