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OLga [1]
3 years ago
6

You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive

the frequency as 1370 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1330 Hz. What is the speed of the police car? The speed of sound in air is 343 m/s.
Physics
1 answer:
swat323 years ago
6 0

Answer:

Explanation:

Given

Apparent  frequency f'=1370\ Hz

Velocity of sound v=343\ m/s

speed of observer v_o=35\ m/s

Using Doppler effect Apparent frequency when source is approaching is given by

f'=f(\frac{v-v_0}{v-v_s})

1370=f(\frac{343-35}{343-v_s})---1

Apparent frequency when source moves away from observer

f''=f(\frac{v+v_0}{v+v_s})

1330=f(\frac{343+35}{343+v_s})---2

Divide 1 and 2 we get

\frac{f'}{f''}=\frac{\frac{343-35}{343-v_s}}{\frac{343+35}{343+v_s}}

\frac{1370}{1330}=\frac{343-35}{343-v_s}\times \frac{343+v_s}{343+35}

v_s=40\ m/s

Thus speed of sound of police car is 40 m/s

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Brrunno [24]

Answer:

Given:

Distance = 35200 miles, time = 2 hr.

So we know = 35200/ 2, = 17600 miles / hr.

8 0
2 years ago
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Find the electron and hole mobilities, and the resistivity of intrinsic silicon at 300K. Is intrinsic silicon a semiconductor
tino4ka555 [31]

Answer:

Resistivity = 231.481 K Ohm

Yes, Intrinsic Silicon is the semiconductor.

Explanation:

Solution:

At 300K:

Let suppose mobility of electron in intrinsic semiconductor = M_{e}

Mobility of electron in intrinsic semiconductor is:

M_{e}  = 1300 cm^{2}/volt.sec

Let suppose mobility of hole in intrinsic semiconductor = M_{h}

M_{h} = 500 cm^{2}/volt.sec

We know that, intrinsic silicon semiconductor has equal number of holes and electrons. So,

At 300 K

Intrinsic Carrier Concentration = 1.5 x 10^{10}/cm^{3} = C

And,

Conductivity of intrinsic Silicon is:

σ = C x (M_{h} + M_{e}) e

e = 1.6 x 10^{-19} C

So, plugging in the values, we get:

σ = C x (M_{h} + M_{e}) e

σ = 1.5 x 10^{10} x (500 + 1300) x 1.6 x 10^{-19}

σ = 4.32 x 10^{-6}

So, now we can find the resistivity.

Resistivity = 1/σ

Resistivity = 1/ 4.32 x 10^{-6}

Resistivity = 231.481 K Ohm

Yes, Intrinsic Silicon is the semiconductor.

7 0
2 years ago
Convert the following to relative uncertainties <br>a) 2.70 ± 0.05cm<br>b) 12.02 ± 0.08cm
DENIUS [597]

data which is expressed in form of following way

a = a_o + \Delta a

here in above expression

a_o = true value

\Delta a = uncertainty in the value

now the relative uncertainty is given as

\frac{\Delta a}{a_o}

now by above formula we can say

a) 2.70 ± 0.05cm

here

True value = 2.70

uncertainty = 0.05

Relative uncertainty = \frac{0.05}{2.70} = 0.0185

b) 12.02 ± 0.08cm

here

True value = 12.02

uncertainty = 0.08

Relative uncertainty = \frac{0.08}{12.02} = 0.00665

4 0
3 years ago
Which best describes a difference between laser light and regular light?
Inga [223]
The basic difference is that the ordinary sources are incoherent that means that the discrete frequencies merge up to give an intermediate between the maximum and minimum frequencies. While the laser is coherent containing the single frequency with maximum amplitude. thus travelling far.
4 0
3 years ago
HELP I NEED THE ANSWER NOW
Setler79 [48]

Answer:

Speed of light

Explanation:

The famous Einstein's equation is:

E=mc^2

where

E is the energy

m is the mass

c=3\cdot 10^8 m/s is the speed of light

In this equation, Einstein summarized the following fact: mass can be converted into energy, and the amount of energy released in such a process is given by the equation.

An example of application of this equation is the nuclear fusion process. In a nuclear fusion, two lighter nuclei combine into a heavier nucleus. However, the mass of the heavier nucleus is slightly less than the sum of the masses of the two original nuclei: some of the mass of the original nuclei has been converted into energy, accorging to the previous equation.

4 0
3 years ago
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