Question

The outstretched hands and arms of a figure skater preparing for a spin can be considered a slender rod pivoting about an axis through its center. (See the figure below (Figure 1).) When the skater's hands and arms are brought in and wrapped around his body to execute the spin, the hands and arms can be considered a thin-walled hollow cylinder. His hands and arms have a combined mass of 7.5 kgkg . When outstretched, they span 1.8 mm ; when wrapped, they form a cylinder of radius 25 cmcm .

The moment of inertia about the axis of rotation of the remainder of his body is constant and equal to 0.35 kg⋅m2kg⋅m2 If the skater's original angular speed is 0.45 rev/srev/s , what is his final angular speed?

Answer #1

The outstretched hands and arms of a figure skater preparing for
a spin can be considered a slender rod pivoting about an axis
through its center (Figure 1). When his hands and arms are brought
in and wrapped around his body to execute the spin, the hands and
arms can be considered a thin-walled hollow cylinder. His hands and
arms have a combined mass 8.0 kg . When outstretched, they span 1.7
m ; when wrapped, they form a thin-walled...

A figure skater is spinning slowly with arms outstretched. He
brings his arms in close to his body and his angular velocity
changes by a factor of 2. By what factor does his moment of inertia
change, and why?

When a figure skater goes into spin she will begin with her arms
extended, and then draws her arms inward. As a result the ice
skater spins faster. Describe why this works in terms of angular
momentum.
Provide your own example of the conservation of linear momentum
in a collision. Use the words elastic, inelastic, and totally
inelastic in your explanation.

What is the angular momentum of a figure skater spinning at
3.2rev/s with arms in close to her body, assuming her to be a
uniform cylinder with a height of 1.5m , a radius of 16cm , and a
mass of 55kg?
How much torque is required to slow her to a stop in 4.4s ,
assuming she does not move her arms?

Biomedical measurements show that the arms and hands together
typically make up 13.0 %% of a person's mass, while the legs and
feet together account for 37.0 %%. For a rough (but reasonable)
calculation, we can model the arms and legs as thin uniform bars
pivoting about the shoulder and hip, respectively. Let us consider
a 70.0 kgkg person having arms 66.0 cmcm long and legs 95.0 cmcm
long. The person is running at 12.0 km/hkm/h, with his arms and...

What is the angular momentum of a figure skater spinning at 2.3
rev/s with arms in close to her body, assuming her to be a uniform
cylinder with a height of 1.5 m, a radius of 16 cm , and a mass of
49 kg ?
How much torque(in magnitude) is required to slow her to a stop
in 4.8 s , assuming she does not move her arms?

a. What is the angular momentum of a figure skater spinning at
2.0 rev/s with arms in close to her body, assuming her to be a
uniform cylinder with a height of 1 m, a radius of 0.2 m, and a
mass of 50 kg?
b. How much torque is required to slow her to a stop in 5.0 s,
assuming she does not move her arms?

A skater spins with angular velocity of 12 rad/s with
his arms extended. How fast will he spin with his arms byhis sides?
Treat the skater’s body as a uniform cylinder of radius R = (your
student number) cm; approximate his armsas uniform rods of length L
= 40 cm and mass m = 4.5 kg. His total mass excluding arms is M =
80 kg.
Student number is 9

Diana, a figure skater, is initially spinning at an angular
speed 2.50 rev/s, with her arms and legs inward. Assume that she is
a uniform cylinder with a height of 1.4 m, a radius of 18 cm, and a
mass of 55 kg. Assume no external torques act.
a) What is her moment of inertia?
b) If she extends her arms outward, what is her new moment of
inertia? Assume that
her armspan is 1.3 m and her arms are...

In this example we see how a system can have constant angular
momentum without having a constant angular velocity! A physics
professor stands at the center of a turntable, holding his arms
extended horizontally, with a 5.0 kgkg dumbbell in each hand
(Figure 1). He is set rotating about a vertical axis, making one
revolution in 2.0 ss. His moment of inertia (without the dumbbells)
is 3.4 kg⋅m2kg⋅m2 when his arms are outstretched, and drops to 1.8
kg⋅m2kg⋅m2 when his...

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