Question

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 legs each swinging through ±30∘±30∘ in 12s12s. Assume that the arms and legs are kept straight.

What is the average angular velocity of his arms and legs?

Using the average angular velocity from Part A, calculate the amount of rotational kinetic energy in this person's arms and legs as he walks.

What is the total kinetic energy due to both his forward motion and his rotation?

What percentage of his kinetic energy is due to the rotation of his legs and arms?

Answer #1

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 74.0 kg person having arms 70.0 cm long and legs 90.0 cm long.
The person is running at 12.0 km/h , with his...

If a person of mass M simply moved forward with speed
V, his kinetic energy would be 12MV2.
However, in addition to possessing a forward motion, various parts
of his body (such as the arms and legs) undergo rotation.
Therefore, his total kinetic energy is the sum of the energy from
his forward motion plus the rotational kinetic energy of his arms
and legs. The purpose of this problem is to see how much this
rotational motion contributes to the...

On average, both arms and hands together account for 13 % of a
person's mass, while the head is 7.0 % and the trunk and legs
account for 80 % . We can model a spinning skater with her arms
outstretched as a vertical cylinder (head, trunk, and legs) with
two solid uniform rods (arms and hands) extended horizontally.
Suppose a 70.0 kg skater is 1.80 m tall, has arms that are each
70.0 cm long (including the hands), and...

On average, both arms and hands together account for 13% of a
person's mass, while the head is 7.0% and the trunk and legs
account for 80%. We can model a spinning skater with her arms
outstretched as a vertical cylinder (head, trunk, and legs) with
two solid uniform rods (arms and hands) extended horizontally.
Suppose a 60.0 kg skater is 1.60 m tall, has arms that are each
74.0 cm long (including the hands), and a trunk that can...

On average, both arms and hands together account for 13%13% of a
person's mass, while the head is 7.0%7.0% and the trunk and legs
account for 80%.80%. We can model a spinning skater with her arms
outstretched as a vertical cylinder (head, trunk, and legs) with
two solid uniform rods (arms and hands) extended horizontally.
Suppose a 75.0 kg75.0 kg skater is 1.50 m1.50 m tall, has arms
that are each 74.0 cm74.0 cm long (including the hands), and a...

On average, both arms and hands together account for 13 % of a
person's mass, while the head is 7.0 % and the trunk and legs
account for 80 % . We can model a spinning skater with her arms
outstretched as a vertical cylinder (head, trunk, and legs) with
two solid uniform rods (arms and hands) extended horizontally.
Suppose a 73.0 kg skater is 1.60 m tall, has arms that are each
68.0 cm long (including the hands), and...

On average, both arms and hands together account for 13% of a
person's mass, while the head is 7.0% and the trunk and legs
account for 80%. We can model a spinning skater with her arms
outstretched as a vertical cylinder (head, trunk, and legs) with
two solid uniform rods (arms and hands) extended horizontally.
Suppose a 63.0 kg skater is 1.60 m tall, has arms that are each
64.0 cm long (including the hands), and a trunk that can...

On average, both arms and hands together account for 13% of a
person's mass, while the head is 7.0% and the trunk and legs
account for 80%. We can model a spinning skater with her arms
outstretched as a vertical cylinder (head, trunk, and legs) with
two solid uniform rods (arms and hands) extended horizontally.
Suppose a 63.0 kg skater is 1.70 m tall, has arms that are each
64.0 cm long (including the hands), and a trunk that can...

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