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3 years ago

14

Calculate the recombination rate if the excess carrier concentration is 1014cm-3 and the carrier lifetime is 1usec. (a) 108 (b)

1010 (c) 1020 (d) 1014

1 answer:

Drupady [299]3 years ago

5 0

Answer:

$10^{20}\frac{cm^{-3}}{sec}$

Explanation:

The recombination rate is denoted by R it is the ratio of excess carrier concentration and life time

The recombination rate R is given by $R=\frac{\Delta n}{\tau _n}$

We have given excess carrier concentration = $10^{14}cm^-3$

Life time $\tau _n=10^{-6}sec$

So recombination rate $R=\frac{\Delta n}{\tau _n}=\frac{10^{14}}{10^{-6}}=10^{20}\frac{cm^{-3}}{sec}$

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The current theory of the structure of the

Mariana [72]

Answers:

a) $2.82(10)^{21} kg$

b) $1410 J$

c) $36.62 m/s$

Explanation:

<h3>a) Mass of the continent</h3>

Density $\rho$ is defined as a relation between mass $m$ and volume $V$ :

$\rho=\frac{m}{V}$ (1)

Where:

$\rho=2720 kg/m^{3}$ is the average density of the continent

$m$ is the mass of the continent

$V$ is the volume of the continent, which can be estimated is we assume it as a a slab of rock 5300 km on a side and 37 km deep:

$V=(length)(width)(depth)=(5300 km)(5300 km)(37 km)=1,030,330,000 km^{3} \frac{(1000 m)^{3}}{1 km^{3}}=1.03933(10)^{18} m^{3}$

Finding the mass:

$m=\rho V$ (2)

$m=(2720 kg/m^{3})(1.03933(10)^{18} m^{3})$ (3)

$m=2.82(10)^{21} kg$ (4) This is the mass of the continent

<h3>b) Kinetic energy of the continent</h3>

Kinetic energy $K$ is given by the following equation:

$K=\frac{1}{2}mv^{2}$ (5)

Where:

$m=2.82(10)^{21} kg$ is the mass of the continent

$v=4.8 \frac{cm}{year} \frac{1 m}{100 cm} \frac{1 year}{365 days} \frac{1 day}{24 hours} \frac{1 hour}{3600 s}=1(10)^{-9} m/s$ is the velocity of the continent

$K=\frac{1}{2}(2.82(10)^{21} kg)(1(10)^{-9} m/s)^{2}$ (6)

$K=1410 J$ (7) This is the kinetic energy of the continent

<h3>c) Speed of the jogger</h3>

If we have a jogger with mass $m=77 kg$ and the same kinetic energy as that of the continent $1413 J$ , we can find its velocity by isolating $v$ from (5):

$v=\sqrt{\frac{2 K}{m}}$ (6)

$v=\sqrt{\frac{2 (1413 J)}{77 kg}}$

Finally:

$v=36.62 m/s$ This is the speed of the jogger

5 0

3 years ago

A 500-g lump of clay is dropped onto a 1-kg cart moving at 60 cm/s. The clay is moving downward at 30 cm/s just before l dith t

viktelen [127]

Answer:

The speed of the cart and clay after the collision is 50 cm/s .

Explanation:

Given :

Mass of lump , m = 500 g = 0.5 kg .

Velocity of lump , v = 30 cm/s .

Mass of cart , M = 1 kg .

Velocity of cart , V = 60 cm/s .

We know by conservation of momentum :

$mv+MV=(m+M)v'$

Here , $v'$ is the speed of the cart and clay after the collision .

Putting all value in above equation .

We get :

$0.5\times 30+1\times 60=(0.5+1)\times v'\\\\v'=\dfrac{15+60}{1.5}\\\\v'=50\ cm/s$

Hence , this is the required solution .

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3 years ago

A 60-kg block initially at rest on a frictionless horizontal surface is acted upon by a force of 3.0 N for a distance of 7.0 m.

Schach [20]

Answer:

Explanation:

Kinetic energy generated = work done by force = force x displacement

= 3 x 7 = 21 J

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3 years ago

An airplane cruises at 900 km/h relative to the air. It is flying from Denver, Colorado, due west to Reno, Nevada, a distance of

Ulleksa [173]

Answer:

26.5 minutes

Explanation:

When the airplane is flying due West from Denver to Reno, the due-East wind with speed of 80km/h would reduce the ground speed by 80 km/h.

Its Denver to Reno ground speed is 900 - 80 = 720 km/h

The time it takes to cover 1200km at this speed is 1200 / 720 = 1.67 hours

On the other hand, when it returns from Reno to Denver in the due-East direction, the due-East wind with speed of 80km/h would add to the ground speed by 80 km/h

Its Reno to Denver ground speed is 900 + 80 = 980 km/h

The time it takes to cover 1200 km at this speed is 1200 / 980 = 1.22 hours

The difference it flight time would be 1.67 - 1.22 = 0.44 hours or 26.5 minutes

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3 years ago

A car accelerates uniformly from rest to a speed of 6.6 m/s in 6.5 s. Find the acceleration the car presents during this time?

Art [367]

Answer:

1.02 m/s²

Explanation:

The following data were obtained from the question:

Initial velocity (u) = 0 m/s

Final velocity (v) = 6.6 m/s

Time (t) = 6.5 s

Acceleration (a) =.?

Acceleration can simply be defined as the change of velocity with time. Mathematically, it can be expressed as:

a = (v – u) / t

Where:

a is the acceleration.

v is the final velocity.

u is the initial velocity.

t is the time.

With the above formula, we can obtain the acceleration of the car as follow:

Initial velocity (u) = 0 m/s

Final velocity (v) = 6.6 m/s

Time (t) = 6.5 s

Acceleration (a) =.?

a = (v – u) / t

a = (6.6 – 0) / 6.5

a = 6.6 / 6.5

a = 1.02 m/s²

Therefore, the acceleration of the car is 1.02 m/s²

3 0

3 years ago