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4 years ago

Can someone answer these?

Physics

1 answer:

natita [175]4 years ago

4 0

Short Answer

3: C

4: D

Problem Three

Remark

Somewhere we ought to be told that this is the Doppler Effect. I have never done a problem using this formula, so I think I'm doing it correctly, but no guarantees. My guess is that the frequency increases as it comes towards you and decreases as it moves away from you. I think that is correct.

Formula

Givens

f' = observed frequency
f = actual frequency
v = velocity of sound or light waves.
vo = velocity of observer (in both cases 0)
vs = velocity of source.

f' = (v + vo) * f / (v - vs)

Solution

v = 3*10^8 m/s
f' = 1.1 f
f = f
vo = 0 We are standing still while all this is going on.
vs = ???

f'/f = 1.1

1.1 = (3*10^8 + 0 ) / (3*10^8 - vs)

3.3*10^8 - 1.1*vs = 3*10^8

3.3*10^8 - 3*10^8= 1.1 vs

0.3 * 10^8 = 1.1 vs

2.73 * 10^7 = vs

The closest answer is 3.00 * 10^7 which is C

Problem Four

Here what is happening is that you are looking for the frequency resulting from a wave moving towards you at 1/2 the speed of sound. You are not moving.

Givens

v = v
vs = 1/2 v
f ' = ?
f = 1000 hz
vo =0

f' = v/(v - 1/2v) * 1000

f' = v/ (1/2 v) * 1000

f' = 2 * 1000

f' = 2000 which is D

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The students conclusion is wrong.

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The students conclusion is wrong because liquids can not soak into concrete. The water evaporated because it was a hot sunny day. The water turned into a gas called water vapor.

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3 years ago

a grinding wheel is initially rotating with an angular velocity 5500 rad/srad/s when its motor is suddenly turned off. it comes

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The angle through which the grinding wheel rotates in the first second = 5300 rad

Angular velocity is, the time charge at which an object rotates, or revolves, about an axis, or at which the angular displacement between our bodies changes. within the discern, this displacement is represented via the angle θ among a line on one body and a line on the alternative.

The angular velocity is described as the charge of trade of the angular position of a rotating body. Linear speed is defined because the charge of change of displacement with respect to time whilst the item moves alongside a straight course.

Initial angular velocity of the grinding wheel = ω1 = 5500 rad/s

Final angular velocity of the grinding wheel = ω2 = 0 rad/s (Comes to rest)

Time is taken by the grinding wheel to come to rest = T = 10 sec

Angular acceleration of the grinding wheel = α

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0 = 5500 + α(10)

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Negative as it is deceleration.

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Learn more about angular velocity here:-brainly.com/question/6860269

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1 year ago

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A microwave oven operating at 1.22 × 108 nm is used to heat 165 mL of water (roughly the volume of a teacup) from 23.0°C to 100.

ANTONII [103]

Answer: The number of photons are $3.7\times 10^8$

Explanation:

We are given:

Wavelength of microwave = $1.22\times 10^8nm=0.122m$ (Conversion factor: $1m=10^9nm$ )

To calculate the energy of one photon, we use Planck's equation, which is:

$E=\frac{hc}{\lambda}$

where,

h = Planck's constant = $6.625\times 10^{-34}J.s$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength = 0.122 m

Putting values in above equation, we get:

$E=\frac{6.625\times 10^{-34}J.s\times 3\times 10^8m/s}{0.122m}\\\\E=1.63\times 10^{-24}J$

Now, calculating the energy of the photon with 88.3 % efficiency, we get:

$E=1.63\times 10^{-24}\times \frac{88.3}{100}=1.44\times 10^{-24}J$

To calculate the mass of water, we use the equation:

$Density=\frac{Mass}{Volume}$

Density of water = 1 g/mL

Volume of water = 165 mL

Putting values in above equation, we get:

$1g/mL=\frac{\text{Mass of water}}{165mL}\\\\\text{Mass of water}=165g$

To calculate the amount of energy of photons to raise the temperature from 23°C to 100°C, we use the equation:

$q=mc\Delta T$

where,

m = mass of water = 165 g

c = specific heat capacity of water = 4.184 J/g.°C

$\Delta T$ = change in temperature = $T_2-T_1=100^oC-23^oC=77^oC$

Putting values in above equation, we get:

$q=165g\times 4.184J/g.^oC\times 77^oC\\\\q=53157.72J$

This energy is the amount of energy for 'n' number of photons.

To calculate the number of photons, we divide the total energy by energy of one photon, we get:

$n=\frac{q}{E}$

q = 53127.72 J

E = $1.44\times 10^{-24}J$

Putting values in above equation, we get:

$n=\frac{53157.72J}{1.44\times 10^{-24}J}=3.7\times 10^{28}$

Hence, the number of photons are $3.7\times 10^8$

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3 years ago

A capacitor consists of two metal surfaces separated by an insulating layer. A new capacitor has no charge on either of its surf

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<h2>Answer:</h2><h3>(A) the positively charged surface increases and the energy stored in the capacitor increases.</h3>

When charging a capacitor transferring charge from one surface to the other, the first surface becomes negatively charged while the second surface becomes positively charged. As you transfer the charge, the voltage of the positively charged surface increases and the energy stored in the capacitor also increases. We can solve this by the definition of capacitance that is a measure of the ability of a capacitor to store energy. For any capacitor, the capacitance is a constant defined as:

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To maintain $C$ constant, if Q increases V also increases.

On the other hand, the potential energy $U$ can be expressed as:

$U=\frac{Q^{2}}{2C}$

In conclusion, as Q increases the potential energy also increases.

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3 years ago