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Alex
3 years ago
13

Calculate the number of free electrons per cubic meter for some hypothetical metal, assuming that there are 1.3 free electrons p

er metal atom. The electrical conductivity and density are 6.8 × 107 (Ω-m)-1 and 10.5 g/cm3, respectively, and its atomic weight is 107.87 g/mol. Use scientific notation.
Physics
1 answer:
boyakko [2]3 years ago
6 0

Answer:

The number of free electrons per cubic meter is 7.61\times 10^{28}\ m^{-3}

Explanation:

It is given that,

The number of free electrons per cubic meter is, 1.3

Electrical conductivity of metal, \sigma=6.8\times 10^7\ \Omega^{-1}m^{-1}

Density of metal, \rho=10.5\ g/cm^3

Atomic weight, A = 107.87 g/mol

Let n is the number of  free electrons per cubic meter such that,

n=1.3\ N

n=1.3(\dfrac{\rho N_A}{A})

Where

\rho is the density of silver atom

N_A is the Avogadro number

A is the atomic weight of silver

n=1.3\times (\dfrac{10.5\ g/cm^3\times 6.02\times 10^{23}\ atoms/mol}{107.87\ g/mol})

n=7.61\times 10^{22}\ cm^{-3}

or

n=7.61\times 10^{28}\ m^{-3}

Hence, this is the required solution.

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A submarine is 20m below the surface of the sea. the pressure due to the water at this depth is P. on another day, the submarine
satela [25.4K]

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1.7p

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3 years ago
A car is traveling at 15 m/sm/s . Part A How fast would the car need to go to double its kinetic energy
GREYUIT [131]

Answer:

21.21 m/s

Explanation:

Let KE₁ represent the initial kinetic energy.

Let v₁ represent the initial velocity.

Let KE₂ represent the final kinetic energy.

Let v₂ represent the final velocity.

Next, the data obtained from the question:

Initial velocity (v₁) = 15 m/s

Initial kinetic Energy (KE₁) = E

Final final energy (KE₂) = double the initial kinetic energy = 2E

Final velocity (v₂) =?

Thus, the velocity (v₂) with which the car we travel in order to double it's kinetic energy can be obtained as follow:

KE = ½mv²

NOTE: Mass (m) = constant (since we are considering the same car)

KE₁/v₁² = KE₂/v₂²

E /15² = 2E/v₂²

E/225 = 2E/v₂²

Cross multiply

E × v₂² = 225 × 2E

E × v₂² = 450E

Divide both side by E

v₂² = 450E /E

v₂² = 450

Take the square root of both side.

v₂ = √450

v₂ = 21.21 m/s

Therefore, the car will travel at 21.21 m/s in order to double it's kinetic energy.

8 0
3 years ago
An unruly student with a spitwad (a lump of wet paper) of mass 20 g in his pocket finds himself in the school library where ther
jeka94

Answer:

T = 188.5 s, correct is  C

Explanation:

This problem must be worked on using conservation of angular momentum. We define the system as formed by the fan and the paper, as the system is isolated, the moment is conserved

         

initial instant. Before the crash

        L₀ = r m v₀ + I₀ w₀

the angular speed of the fan is zero w₀ = 0

final instant. After the crash

        L_f = I₀ w + m r v

        L₀ = L_f

        m r v₀ = I₀ w + m r v

angular and linear velocity are related

        v = r w

        w = v / r

        m r v₀ = I₀ v / r + m r v

         m r v₀ = (I₀ / r + mr) v

       v = \frac{m}{\frac{I_o}{r}  +mr} \ r v_o

let's calculate

       v = \frac{0.020}{\frac{1.4}{0.6  } + 0.020 \ 0.6  } \ 0.6 \ 4

       v = \frac{0.020}{2.345} \ 2.4

       v = 0.02 m / s

         

To calculate the time of a complete revolution we can use the kinematics relations of uniform motion

        v = x / T

         T = x / v

the distance of a circle with radius r = 0.6 m

         x = 2π r

we substitute

         T = 2π r / v

let's calculate

         T = 2π 0.6/0.02

         T = 188.5 s

reduce

         t = 188.5 s ( 1 min/60 s) = 3.13 min

correct is  C

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3 years ago
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boyakko [2]

Explanation:

It is given that,

Displacement of the delivery truck, d_1=3.2\ km (due east)

Then the truck moves, d_2=2.45\ km (due south)

Let d is the magnitude of the truck’s displacement from the warehouse. The net displacement is given by :

d=\sqrt{d_1^2+d_2^2}

d=\sqrt{3.2^2+2.45^2}

d = 4.03 km

Let \theta is the direction of the truck’s displacement from the warehouse from south of east.

\theta=tan^{-1}(\dfrac{2.45}{3.2})

\theta=37.43^{\circ}

So, the magnitude and direction of the truck’s displacement from the warehouse is 4.03 km, 37.4° south of east.

8 0
3 years ago
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