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True [87]
3 years ago
15

We can look at the band structure of an element to get an idea of how many electronsper atom participate in conduction. We can a

lso determine this numberbased on the free electron density, the atomic mass, and the mass density of thematerial.Calculate the free electron density of lithium. The Fermi energy is 4.72 eV.
Physics
1 answer:
Natasha_Volkova [10]3 years ago
4 0

Answer:

the free electron density of lithium is 2.3 × 10²⁸ /m³

Explanation:

The Fermi energy is 4.72 eV.

The Fermi energy (highest filled orbital energy ) of free electron is

\varepsilon_f=\frac{h^2}{8m_e} (\frac{3N}{\pi V} )^{2/3}

Rearrange the above equation for free electron density of lithium

\frac{N}{V} = \frac{\pi }{3} (\frac{8m_e \varepsilon_f}{h^2} )^{3/2}

where,

h = 6.626 × 10⁻³⁴J.s

m_e = 9.11 × 10⁻³¹kg

\varepsilon_f = 4.72eV

= \frac{\pi }{3} (\frac{8(9.11\times10^{-31})(4.72\times1.6\times10^{-19})}{6.626\times10^{-34}} )\\\\= 2.3\times10^{28} /m^3

Thus, the free electron density of lithium is 2.3 × 10²⁸ /m³

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You are trying to hear your friend give directions to new store in town. But from your distance (1 point) of 15 m you only hear
Marat540 [252]

Answer:

option D

Explanation:

given,

Intensity of sound = 20 dB

distance = 15 m

intensity of sound is increased to = 50 dB

distance between the sound level = ?

Using relation

L_2 = L_1 - |20(log \dfrac{r_2}{r_1})|

L₁ = 20 dB        L₂ = 50 dB         r₁ = 15 m      r₂ = ?

log (\dfrac{r_2}{r_1}) = \dfrac{L_1 -L_2}{20}

\dfrac{r_2}{r_1}= 10^{\dfrac{|L_1 -L_2|}{20}}

r_2 =r_1 10^{\dfrac{|L_1 -L_2|}{20}}

r_2 =15 \times 10^{\dfrac{|20-50|}{20}}

r_2 =15 \times 10^{-1.5}

r₂ = 0.47 m

r₂ = 47 cm

hence, the correct answer is option D

7 0
3 years ago
A 100-N force causes an object to<br> accelerate at 2 m/s/s. What is the<br> mass of the object?
Kitty [74]

Answer:

50\; \rm kg.

Explanation:

By Newton's Second Law, the acceleration a of an object is proportional to the net force \sum F on it. In particular, if the mass of the object is m, then

\sum F = m \cdot a.

Rewrite this equation to obtain:

\displaystyle m = \frac{\sum F}{a}.

In this case, the assumption is that the 100\; \rm N force is the only force that is acting on the object. Hence, the net force \sum F on the object would also be

Make sure that all values are in their standard units. Forces should be in Newtons (same as \rm kg \cdot m \cdot s^{-2}, and the acceleration of the object should be in meters-per-second-squared (\rm m \cdot s^{-2}). Apply the equation \displaystyle m = \frac{\sum F}{a} to find the mass of the object.

\displaystyle m = \frac{100\; \rm N}{2\; \rm m \cdot s^{-2}} = 50\; \rm kg.

4 0
3 years ago
3. Learn: Energy is transferred along food chains, however, the amount of available energy decreases from one
Zolol [24]

''Energy is destroyed because animals are higher levels do not need as much energy'' is not the valid reason.

<h3>What is respiration?</h3>

Respiration is the cellular process of releasing energy from food. Some of the energy released is used to produce ATP. 90 percent of energy is lost as heat energy whereas 10 percent energy is transferred to other trophic levels.

So we can conclude that ''Energy is destroyed because animals are higher levels do not need as much energy'' is not the valid reason.

Learn more about energy here: brainly.com/question/19666326

8 0
2 years ago
Could friction
ziro4ka [17]

Answer:

Friction:  is used to hang an object on the wall

  Force: is what will determine if the object stays in place or not  

Explanation:

5 0
3 years ago
Em um centro de distribuição uma empilhadeira carrega uma caixa de 1000kg até o caminhão responsável pelo transporte desta carga
Yakvenalex [24]

Answer:

F = 592238.09 N

Explanation:

To find the mean force you first calculate the acceleration by using the following kinematic equation:

v^2=v_o^2+2ax\\\\v_o=0m/s\\\\v=10km/h\\\\x=8.4m\\\\

you do "a" the subject of the equation and replace the values of the other parameters:

a=\frac{v^2}{2x}=\frac{10000m/s}{2(8.4m)}=595.23\frac{m}{s^2}

next, the force, by using the second Newton law is:

F=ma=(1000kg)(595.23\frac{m}{s^2})=595238.09\ N

hence, the force is 592238.09 N

- - - - - - - - - - - - - - - - - - - - - - - - - - -

TRANSLATION:

Para encontrar a força média, primeiro calcule a aceleração usando a seguinte equação cinemática:

você faz "a" o assunto da equação e substitui os valores dos outros parâmetros:

Em seguida, a força, usando a segunda lei de Newton, é:

portanto, a força é 592238.09 N

8 0
3 years ago
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