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Karolina [17]
3 years ago
8

Your boss asks you to design a room that can be as soundproof as possible and provides you with three samples of material. The o

nly information on each sample's label is the material's coefficient of absorption. The coefficient of absorption listed on Sample A is 30%, on Sample B is 47%, and on Sample C is 62%. When your boss asks for your choice and the reasoning behind it, what would you tell him?
A. Sample C would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest.

B. Sample A would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the largest.

C. Sample C would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the largest.

D. Sample A would be best, because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest.
Physics
2 answers:
ivolga24 [154]3 years ago
8 0

The correct answer is A.

The coefficient of absorption of material A is 30%. So, the material will absorb 30% energy of the incident wave falling on it. Thus, the reflected wave will carry the rest 70% energy.

The coefficient of absorption of material B is 47%. So, the material will absorb 47% energy of the incident wave falling on it. Thus, the reflected wave will carry the rest 53% energy.

The coefficient of absorption of material C is 62%. So, the material will absorb 62% energy of the incident wave falling on it. Thus, the reflected wave will carry the rest 28% energy.

Hence, material C would be the best, because the percentage of the energy in an incident wave that remains in a reflected wave from this material is the smallest.

timurjin [86]3 years ago
7 0
I believe the answer is A
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Two balloons are charged with an identical quantity and type of charge: -4 nc They are held apart at a separation distance of 70
blagie [28]

Answer:

29.4 uN

Explanation:

The electric force between two charges can be calculated using Coulomb's Law. According to this law the force between two point charges is given as:

F=k\frac{q_{1} q_{2} }{r^{2}}

where k is a proportionality constant known as the Coulomb's law constant. Its value is 9 \times 10^{9} Nm²/C²

r = distance between charges = 70 cm = 0.7 m

q1 = q2 = 4nC = 4 \times 10^{-9} C

The negative sign indicates that the charges are negative. In the formula we will only use the magnitude of the charges.

Using these values in the formula, we get:

F=9 \times 10^{9} \times \frac{4 \times 10^{-9} \times 4 \times 10^{-9}}{0.7^{2}}\\\\ F=2.94\times10^{-7} N\\\\ F=29.4 \times 10^{-6} N\\\\ F=29.4 \mu N

Therefore, the magnitude of repulsive force between the given charges will be 29.4 uN

8 0
3 years ago
By which method does the following move into the cell: movement of oxygen, carbon dioxide, and other small uncharged molecules a
Gwar [14]
Oxygen, Carbon dioxide and other small uncharged molecules can move through the cell membrane through a method called osmosis 
osmosis is when there is a semipermeable membrane and molecules pass through it, where there is less concentration of molecules.
3 0
3 years ago
A rectangular certificate has a perimeter of 32 inches. Its area is 63 square inches. What are the dimensions of the certificate
irina1246 [14]
Perimeter = 2 ( L + W )
32 = 2 ( L + W )
16 = L + W
L = 16 - W

Area = L W
63 = L W
63 = (16-W) W
63 = 16W - W²
-W² + 16 W - 63 = 0
By factorizing W = 9 or W = 7
So the dimensions are 7 and 9
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3 years ago
A straight wire of length 0.62 m carries a conventional current of 0.7 amperes. What is the magnitude of the magnetic field made
anyanavicka [17]

Answer:

Magnetic field at point having a distance of 2 cm from wire is 6.99 x 10⁻⁶ T

Explanation:

Magnetic field due to finite straight wire at a point perpendicular to the wire is given by the relation :

B=\frac{\mu_{0}I }{2\pi R }\times\frac{L}{\sqrt{L^{2}+R^{2}  } }      ......(1)

Here I is current in the wire, L is the length of the wire, R is the distance of the point from the wire and μ₀ is vacuum permeability constant.

In this problem,

Current, I = 0.7 A

Length of wire, L = 0.62 m

Distance of point from wire, R = 2 cm = 2 x 10⁻² m = 0.02 m

Vacuum permeability, μ₀ = 4π x 10⁻⁷ H/m

Substitute these values in equation (1).

B=\frac{4\pi\times10^{-7}\times  0.7 }{2\pi \times0.02 }\times\frac{0.62}{\sqrt{(0.62)^{2}+(0.02) ^{2}  } }

B = 6.99 x 10⁻⁶ T

3 0
3 years ago
In a physics laboratory experiment, a coil with 200 turns enclosing an area of 13.1 cm2 is rotated during the time interval 3.10
sergij07 [2.7K]

Answer:

A)\Phi=83.84\times 10^{-9}

B)\Phi=0 Wb

C)emf=5.4090\times 10^{-4}V

Explanation:

Given that:

  • no. of turns i the coil, n=200
  • area of the coil, a=13.1 \times 10^{-4}\,m^2
  • time interval of rotation, t=3.1\times 10^{-2}\,s
  • intensity of magnetic field, B=6.4\times 10^{-5}\,T

(A)

Initially the coil area is perpendicular to the magnetic field.

So, magnetic flux is given as:

\Phi=B.a\,cos \theta..................................(1)

\theta is the angle between the area vector and the magnetic field lines. Area vector is always perpendicular to the area given. In this case area vector is parallel to the magnetic field.

\Phi=6.4\times 10^{-5}\times 13.1 \times 10^{-4}\, cos 0^{\circ}

\Phi=83.84\times 10^{-9} Wb

(B)

In this case the plane area is parallel to the magnetic field i.e. the area vector is perpendicular to the magnetic field.

∴  \theta=90^{\circ}

From eq. (1)

\Phi=6.4\times 10^{-5}\times 13.1 \times 10^{-4}\, cos 90^{\circ}

\Phi=0 Wb

(C)

According to the Faraday's Law we have:

emf=n\frac{B.a}{t}

emf=\frac{200\times 6.4\times 10^{-5}\times 13.1 \times 10^{-4}}{3.1\times 10^{-2}}

emf=5.4090\times 10^{-4}V

7 0
3 years ago
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