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mars1129
23 hours ago
10

As a rough approximation, the human body may be considered to be a cylinder of length L=2.0m and circumference C=0.8m. (To simpl

ify things, ignore the circular top and bottom of the cylinder, and just consider the cylindrical sides.) If the emissivity of skin is taken to be e=0.6, and the surface temperature is taken to be T=30∘C, how much thermal power P does the human body radiate?
Physics
1 answer:
inna [2.2K]23 hours ago
4 0
Thermal Power is approximately 460W. According to the Stephan-Boltzmann Law Formula: P = єσT⁴A, where: P = radiation energy, σ = Stefan-Boltzmann Constant, T = absolute temperature in Kelvin, є = emissivity of the material, and A = the surface area. Given that σ = 5.67 x 10^(-8), ε = 0.6, and T = 30°C which converts to Kelvin as 303K, with the human body dimensions of 2m length and 0.8m circumference leading to an area of 1.6m², so thermal power equals 0.6 x 5.67 x 10^(-8) x 303⁴ x 1.6 = 458.8W. Rounding gives about 460W.
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Suppose that an owner of the same dog breed has also taken some measurements. They notice that the surface area of the dog has i
inna [2205]

Answer:

The surface area of the dog changes from A to 3A

Explanation:

It is stated that the dog's surface area has increased by a factor of 3 over four years.

We need to calculate the change in the relative surface area of the dog over this timeframe.

Let’s assume the initial surface area is A.

Since the surface area has been multiplied by 3,

it follows that the surface area after four years is equal to 3×A = 3A.

Thus, the dog's surface area transitions from A to 3A.

7 0
15 days ago
Two identical carts travel at the same speed toward each other, and then a collision occurs. The graphs show the momentum of eac
inna [2205]

Explanation:

The term 'collision' refers to the interaction between two objects. There are two distinct types of collisions: elastic and inelastic.

In this scenario, two identical carts are heading towards each other at the same speed, resulting in a collision. In an inelastic collision, the momentum is conserved before and after the incident, but kinetic energy is lost.

After the event, both objects combine and move together at a single velocity.

The graph representing a perfectly inelastic collision is attached, illustrating that both carts move together at the same speed afterward.

5 0
28 days ago
Two vectors A⃗ and B⃗ are at right angles to each other. The magnitude of A⃗ is 4.00. What should be the length of B⃗ so that th
serg [2593]

Answer:

B= \sqrt{65} ≅8.06

Explanation:

Applying the Pythagorean theorem:

C^{2}= A^{2} + B^{2}

Here, C denotes the hypotenuse length, while A and B signify the lengths of the other two sides of the triangle. We can calculate B's length knowing the hypotenuse is 9 and A is 4.

9^{2}=4^{2} + B^{2}

81= 16+ B^{2}

81-16= B^{2}

B= \sqrt{65} ≅8.06

8 0
1 month ago
A 30.0-kg child sits on one end of a long uniform beam having a mass of 20.0 kg, and a 40.0-kg child sits on the other end. The
Softa [2029]

Let "L" denote the beam's length.

According to the diagram:

AD = length of the beam = L

AC = CD = AD/2 = L/2

BC = AC - AB = (L/2) - 1.10

BD = AD - AB = L - 1.10

m = mass of the beam = 20 kg

m₁ = mass of the child at one end = 30 kg

m₂ = mass of the child at the opposite end = 40 kg

By applying the principle of torque equilibrium around point B:

(m₁ g) (AB) = (mg) (BC) + (m₂ g) (BD)

30 (1.10) = (20) ((L/2) - 1.10) + (40) (L - 1.10)

L = 1.98 m

4 0
19 days ago
A 57 kg paratrooper falls through the air. How much force is pulling him down?
serg [2593]
The formula is Force = Mass * acceleration due to gravity. Considering a paratrooper's mass is 57 kg and the acceleration due to gravity is 9.81 m/s², the force acting downwards can be calculated. Therefore, substituting the values gives F = 57 * 9.81, leading to a force of 559.17 N. So, the downward force is 559.17 N.
7 0
9 days ago
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