Consider an ideal intrinsic semiconductor in thermal equilibrium. No external forces or fields are applied to this semiconductor. At temperatures above 0 K, the electron concentration in the conduction band is non-zero because
A: some electrons from dopant atoms will overcome the bandgap by gained thermal energy.
B: some electrons from dopant atoms will overcome the ionization energy by gained thermal energy.
C: some electrons from the conduction band will overcome the bandgap by gained thermal energy.
D: some electrons from the valence band will overcome the bandgap by gained thermal energy.

Answer:

speed = 10.1215 m/s

Explanation:

speed = distance / time

speed = 100 / 9.88 = 10.1215 m/s

ANSWER:

1573.5 g

STEP-BY-STEP EXPLANATION:

Given:

Volume (V) = 150 cm³

We have that the density of silver is 10.49 g/cm³, therefore, we calculate its mass, as follows:

The mass of silver is 1573.5 grams

Explanation:

Sun— Nuclear energy is converted to heat and light energy

Corn absorbs sunlight in order to produce sugars and oxygen for plant growth.

Corn is fermented to produce ethanol, which is burned to power generators to give an electrical current The speaker takes the electrical current and produces sound.

Answer:

sun, corn, corn, speaker

Explanation:

i took the k-12 test! have an amazing day! XX <3

Answer:

By making the object sharp pointed

Answer:

Electromagnetic waves are periodic oscillations in the intensity of an electromagnetic field. OR. An electromagnetic wave is a transverse wave that has electrical and magnetic properties

Answer: The scenario violates the second law of thermodynamics.

Explanation: The second law states that heat cannot be converted into work without some loss of usable energy, and that the amount of usable energy in a closed system will always decrease over time. Therefore, the machine described in the scenario cannot exist because it would violate the second law by converting all of the heat into electricity without any loss of usable energy.

The magnitude of the deceleration of the car will be 3.895 meters per second square.

One dimension denotes mobility in a single direction or in a straight line. Think of a vehicle traveling down a straight road or a person walking on a straight track. Imagine throwing something vertically into the air, then observing it fall.

When the driver suddenly presses the brakes, a car that is now moving at 28.6 m/s begins to slow down steadily. Within 105 meters, the vehicle stops.

v² - u² = 2as

0² - (28.6)² = 2 x a x 105

- 817.96 = 210a

a = - 3.895 meters per second square

The magnitude of the deceleration will be 3.895 meters per second square.

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Answer:

Energy in carriage (Potential energy) = 4,116 J

Explanation:

Given:

Mass of baby = 20 kg

Height = 21 m

Find:

Energy in carriage (Potential energy)

Computation:

The energy accumulated in an object as a result of its location relative to a neutral level is known as potential energy.

In carriage accumulated energy is potential energy.

Energy in carriage (Potential energy) = mgh

Energy in carriage (Potential energy) = (20)(9.8)(21)

Energy in carriage (Potential energy) = 4,116 J

Answer: it would take 4 seconds

Explanation:

Answer:

- They need oxygen to burn fuel

- Aerodynamics

- Extreme temperatures

- Radiation

- Pressure issues

Explanation:

A airplane is a heavier-than-air aircraft kept aloft by the upward thrust exerted by the passing air on its fixed wings and driven by propellers, jet propulsion, etc.

Aeroplanes cannot travel in space for several reasons:

They need oxygen to burn fuel - Aeroplane engines rely on the oxygen in the atmosphere to burn fuel and generate thrust. In space, there is no atmosphere so there is no oxygen for the engines to work.

Aerodynamics - Aeroplane wings generate lift by interacting with the air. In space, there is no air so wings would be unable to generate any lift. Aeroplanes rely on aerodynamics to fly which does not work in space.

Extreme temperatures - In space, temperatures can range from -150 degrees Celsius to 150 degrees Celsius. Aeroplanes are designed to operate within a much narrower temperature range. The extreme cold and heat of space could damage aeroplane components.

Radiation - In space, there are high levels of radiation from the Sun and cosmic rays. Aeroplane bodies are not designed to shield against this type of radiation and it could damage electronics and affect aeroplane systems.

Pressure issues - Aeroplanes are designed to withstand air pressures at altitudes up to around 12 kilometers. In low-Earth orbit and beyond, the air pressure is essentially zero. This extreme change in pressure could cause structural damage to the aeroplane.

In summary, while aeroplanes are designed to fly through the Earth's atmosphere, they lack the key features needed to operate in the extreme environment of outer space like spaceships. Aeroplanes require things like oxygen, aerodynamics and being able to withstand changes in pressure - all of which do not exist or work the same way in space.

Explanation:

The wing is pushed up by the air under it. Large planes can only fly as high as about 7.5 miles. The air is too thin above that height. It would not hold the plane up.

The net displacement of the object from t = 0s to t = 8s is 2 m.

The initial velocity of the object is 1 m/s.

The  final velocity of the object is 0 m/s.

The average velocity of the object from t = 0s to t = 8s is 0.25 m/s.

The distance traveled by the object in the first 8 seconds is 6 m.

The displacement of the object is the change in the position of the object.

d = Δx

d = x(0) = x(8)

d = 2 m - 0 m = 2m

v = x/t

v = 2m / 2 s

v = 1 m/s

v = x/t

v = 0/8 s = 0 m/s

v(avg) = Δx/Δt = 2 m/8 s = 0.25 m/s

in the first 2 seconds = 2 m

in the first 6 seconds = 4 m

in the first 8 seconds = 2 m + 4 m + 0 = 6 m

Thus, the net displacement of the object from t = 0s to t = 8s is 2 m.

The initial velocity of the object is 1 m/s.

The  final velocity of the object is 0 m/s.

The average velocity of the object from t = 0s to t = 8s is 0.25 m/s.

The distance traveled by the object in the first 8 seconds is 6 m.

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Answer:

15.4

Explanation:

Answer is sunlight

Explanation :

Answer:

glucose is needed

Explanation:

I just learnt it last week and here is what it says in my notes.

Oxygen is in,

water is in,

carbon dioxide is in,

engery(which is sunlight) is in,

what is not in is glucose.

Answer:

close to the mirrors surface

Explanation:

this is because angle of incidence equals angle of reflection

Potential energy is stored energy because it has the potential to do something which laters turns into kinetic energy which is the moving energy.

The Falcon 9 rocket is so important in today's space exploration world because It's a reusable rocket and has saved money by being reused over 60 times already.

option D.

The Falcon 9 rocket, is developed by SpaceX, and it holds  a significant importance in today's space exploration world due to several key features and achievements, and some of the importance include the following;

From the given options, we can conclude that the Falcon 9 rocket is so important in today's space exploration world because It's a reusable rocket and has saved money by being reused over 60 times already.

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Answer:

Explanation:

(a) The time necessary for the car to reach the truck can be calculated using the equation for average velocity:

v_avg = v0 + at

where v0 is the initial velocity of the car (which is 0 m/s at the instant the light turns green), a is the acceleration of the car (2.00 m/s^2), and t is the time elapsed.

Since the truck is traveling with a constant velocity of 15.0 m/s, we can equate the average velocity of the car to the velocity of the truck:

v0 + at = 15.0 m/s

Solving for t, we get:

t = (15.0 m/s - v0) / a = 15.0 m/s / 2.00 m/s^2 = 7.50 s

(b) The distance beyond the traffic light that the car will pass the truck can be calculated using the equation for displacement:

d = v0t + 1/2at^2

Plugging in the values we found above, we get:

d = (0 m/s)(7.50 s) + 1/2(2.00 m/s^2)(7.50 s)^2 = 56.25 m

(c) The speed of the car when it passes the truck can be calculated using the equation for velocity:

v = v0 + at = 0 m/s + (2.00 m/s^2)(7.50 s) = 15.0 m/s

As the free magnet is brought slowly approaching the magnet that is fixed, a pull toward the fixed magnet will eventually become apparent.

The region surrounding a magnet that experiences the effects of magnetism is known as the magnetic field. When describing the distribution of the magnetic force within and around a magnetic object in nature, the magnetic field is a useful tool.

Compass, motor, refrigerator magnets, railroad tracks, and modern roller coasters are all examples of objects that use magnetic force. Charges that travel across its areas feel a force. All moving charges produce a magnetic field.

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We can see here that the statement that is correct will be: B. The rock display with larger holes shows petroleum drilling, which is deep underground.

A geologist is a scientist who focuses on the solid components of the Earth, such as minerals and rocks, as well as the processes that shape the planet's surface.

Geologists study the make-up, structure, and past of the Earth's crust in order to comprehend geological processes including mountain creation, earthquake and volcanic activity, and the exploitation of natural resources. They frequently perform fieldwork, gathering samples, running surveys, and researching geological formations.

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The complete question is that:

Your class goes on a field trip to observe drilling machinery. The geologists at the drill site show you displays of drilled rocks to compare different types of drills and methods. The drilled holes in one rock display are significantly larger than the holes drilled in the display next to it. Given this information, which statement is correct? (1 point)

A. The rock display with smaller holes shows copper drilling, which is deep underground.

B. The rock display with larger holes shows petroleum drilling, which is deep underground.

C. The rock display with smaller holes shows petroleum drilling, which is closer to the surface.

D. The rock display with larger holes shows copper drilling, which is closer to the surface.

Solution :

The relationship between the strength of magnetic field and the radiusof a charged particle's path is obtained through Newton's second law, which is given by :

F = ma

F = qvB and \($a=\frac{v^2}{r}$\)

Substituting these values in the second law of Newton,

\($qvB=\frac{mv^2}{r}$\)

Now solving for B, we get:

\($B = \frac{mv}{rq}$\)

  \($=\frac{(1.67 \times 10^{-27})(5 \times 10^{7})}{2\times 1.6 \times 10^{-19}}$\)

 = 0.261 T

The field strength can be obtained by using the technology of today.

Answer:

Net torque in positive direction:

Fz = -450 * cos 30 deg * 1.5 = -585 N-M

Fz = 200 * 3.5 = 700 N-M

Net F = 115 N-M

Torque is generally defined as L = R X F

X cross Y = Z     normal coordinate system

Note that Z will be out of the page giving the positive value for the torque.

To find the mass in kilograms, you need to know the object's weight in newtons and the acceleration due to gravity. The formula for finding mass is mass = weight / acceleration due to gravity. So if you have an object with a weight of 100 N and the acceleration due to gravity is 9.8 m/s^2, the mass would be 10.204 kg.

The mass of the block is 0.025 kg or 25 g, when the spring has k = 28 N/m, and compresses 0.11 m before bringing the block to rest.

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Answer:

k=3; l= -1.

Explanation:

1) if if m=2i-j and n= 4i+3j, then km+ln=2i-6j can be written k(2i-j)+l(4i+3j)=2i-6j;

2) after evoluation of the last expression:

i(2k+4l)+j(-k+3l)=2i-6j - it is possible to make up the system of equations:

\(\left \{ {{2k+4l=2} \atop {-k+3l=-6}} \right. \ = > \ \left \{ {{k=3} \atop {l=-1}} \right.\)

The values of k and l such that km + ln = 2i - 6j is -

k = 3 and I = -1

We have the following two vectors -

m = 2i - j

n = 4i + 3j

We have to find k and l such that km + ln = 2i - 6j

A quantity that has both magnitude and direction is a vector quantity. Example - Force, Displacement, velocity. A vector is represented in the form of its components along the three axes of the coordinate system i.e., x, y and z.

According to the question, we have -

m = 2i - j

n = 4i + 3j

and -

km + ln = 2i - 6j

k (2i - j) + l (4i + 3j) = 2i - 6j

2ik - jk + 4li + 3lj = 2i - 6j

2ik + 4li - jk + 3lj = 2i - 6j

(2k + 4l)i - (k - 3l)j = 2i - 6j

Comparing the equations on both sides, we get -

2k + 4l = 2

k + 2l = 1               (1)

and

k - 3l = 6            (2)

Now -

k + 2l = 1

k = 1 - 2l , using this value in (2), we get -

(1 - 2l) - 3l = 6

1 - 2l - 3l = 6

1 - 5l = 6

1 - 6 = 5l

-5 = 5l

l = -1

Using l = -1 , in the (1) -

k + 2 (-1) = 1

k - 2 = 1

k = 1 + 2

k = 3

Hence, the values of k and l such that km + ln = 2i - 6j is -

k = 3 and I = -1.

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Answer:

the velocity of their combined weight after they collide is 0.39 m/s

Explanation:

From the information given, the kid and granny moved together after collision with a combined velocity. This means that the collision is inelastic. Given that momentum is conserved, for an inelastic collision, we would apply the formula;

m1u1 + m2u2 = (m1 + m2)V

where

m1 is the mass of the skateboard

v1 is the velocity of the skateboard

m2 is the mass of the granny

v2 is the velocity of the granny

V is the velocity of the combined weight

From the information given,

m1 = 13

u1 = 4

m2 = 120

u2 = 0(the granny was at rest)

By substituting these values into the formula, we have

13 x 4 + 120 x 0 = (13 + 120)V

52 = 133V

V = 52/133

V = 0.39 m/s

Answer:

32.25 s

Explanation:

From the question,

P = W/t.............. Equation 1

Where P = Power, W = work done, t = time.

But

W = F×d................. Equation 2

Where F = force and d = distance

Substitute equation 2 into equation 1

P = F×d/t............... Equation 3

make t the subject of euqation 3

t = (F×d)/P............. Equation 4

Givn: F = 150 N, d = 4.3 m, P = 20 watts.

Substitute these values into equation 4

t = (150×4.3)/20

t = 32.25 s

Explanation:

P=E/T

E=15N

T=2s

P=15/2

P=7.5

The question is incomplete. The complete question is :

First Law of Thermodynamics - Sign Convention The first law of thermodynamics applies the conservation of energy principle to systems where heat transfer and doing work are the methods of transferring energy into and out of the system. The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system. In equation form, the first law of thermodynamics is AU = Q-W. Here AU is the change in internal energy U of the system. Q is the net heat transferred into the system that is, Q is the sum of all heat transfer into (positive) and out of (negative) the system. W is the net work done by the system—that is, W is the sum of all work done by (positive) and on (negative) the system. We use the following sign conventions: if Q is positive, then there is a net heat transfer into the system; if W is positive, then there is net work done by the system. So positive Q adds energy to the system and positive W takes energy from the system. Thus AU = Q-W. Note also that if more heat transfer into the system occurs than work done, the difference is stored as internal energy. The first law of thermodynamics AU = 9 - W Ur-U, Heat Work System AU--W system w Qin: talu Qout:

The first law of thermodynamics AU = Q - W U-U Heat Work System AUQ-W Qin: ta Qout: - Wout: + WK w Win: - - volume expands t volume decreases o All answers can be positive or negative. (a) Suppose there is heat transfer of 42 ) into a system, while the system does 6 ) of work. Later, there is heat transfer of 22 J out of the system while 6 ) of work is done on the system. What is the net heat transfer? 20 Correct (100.0%) Submit What is the total work? Enter a number Submit (5 attempts remaining) What is the net change in internal energy of the system? Enter a number

What is the net change in internal energy of the system? Enter a number Submit (5 attempts remaining) (b) What is the change in internal energy of a system when a total of 140 J of heat transfer occurs out of (from) the system and 165 ) of work is done on the system? Enter a number Submit (5 attempts remaining) (c) An athlete doing push-ups performs 645 kJ of work and loses 440 kJ of heat. What is the change in the internal energy (in kJ) of the athlete? Enter a number Submit (5 attempts remaining) kJ (d) An athlete doing push-ups performs 690 kJ of work and loses 450 kJ of heat. Then he takes in 830 kJ of energy from eating food, What is the total change in the internal energy (in kJ) of the athlete? Enter a number kJ.

Solution :

a). Given :

\($Q_1 = 42 \ J$\) , \($Q_2 = -22 \ J , \ W_1 = 6 \ J, \ W_2 = -6 \ J $\)

Net heat transfer

\($Q= Q_1+Q_2$\)

   = 42 + (-22)

   = 20 J

Total work

\($W= W_1+W_2$\)

   = 6 + (-6)

   = 0 J    

∵ ΔU = Q - W

       = 20 - 0

        = 20 J

This is the net change in the internal energy of the system.

b). ΔU = Q + W

           = (-140) + (-165)

           = -305 J

c). ΔU = Q + W

           = (-440) + (645)

           = 205 J

d). ΔU = Q + W

           = (-450) + (690)

           = 240 J

Answer:

the power that can be generated by the river is 117.6 MW

Explanation:

Given that;

Volume flow rate of river v = 240 m³/s

Height above the lake surface a h = 50 m

Amount of power can be generated from this river water after the dam is filled = ?

Now the collected water in the dam contains potential energy which is used for the power generation,

hence, total mechanical energy is due to potential energy alone.

\(E_{mech}\) = m(gh)

first we determine the mass flow rate of the fluid m

m = p×v

where p is density ( 1000 kg/m³

so we substitute

m = 1000kg/m³ × 240 m³/s

m = 240000 kg/s

so we plug in our values into ( \(E_{mech}\) = m(gh) kJ/kg )

\(E_{mech}\) = 240000 × 9.8 × 50

\(E_{mech}\) = 117600000 W

\(E_{mech}\) = 117.6 MW

Therefore, the power that can be generated by the river is 117.6 MW