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Paladinen [302]
3 years ago
12

The universe is filled with photons left over from the Big Bang that today have an average energy of about 4.9 ✕10-4 (correspond

ing to a temperature of 2.7 K).
What is the number of available energy states per unit volume for these photons in an interval of 4 ✕10-5eV?
Physics
1 answer:
motikmotik3 years ago
8 0

Answer:

The number of available energy is 4.820\times10^{45}

Explanation:

Given that,

Energy E=4.9\times10^{-4}\ J

Temperature = 2.7 K

Energy states per unit volume dE=4\times10^{-5}\ eV

We need to calculate the number of available energy

Using formula of energy

N=g(E)dE

N=\dfrac{8\pi\times E^2 dE}{(hc)^3}

Where, h = Planck constant

c = speed of light

E = energy

Put the value into the formula

N=\dfrac{8\pi\times(4.9\times10^{-4})^2\times4\times10^{-5}\times1.6\times10^{-19}}{(6.67\times10^{-34}\times3\times10^{8})^3}

N=4.820\times10^{45}

Hence, The number of available energy is 4.820\times10^{45}

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The fulcrum of a first-class lever divides its 9.0 m arm into two sections—a 6.0 m arm and a 3.0 m arm. You place a rock weighin
nexus9112 [7]
For balancing the lever, force on both the sides shall be equal. so,
Force on 3 m end = m × a = 3 × 98.1 = 294.3

Now, on 6 m end, it would be: = 294.3/6 = 49.05
After rounding-off to the nearest hundredth value, it would be: 49 N

Finally, Option A would be your correct answer.

Hope this helps!
6 0
2 years ago
If two particles have equal charges and are placed near one another, how
navik [9.2K]

Answer: C) The two particles will move away from each other

Explanation:

When two electrically charged bodies come closer, appears a force that attracts or repels them, depending on the sign of the charges of this two bodies.

This is stated by Coulomb's Law:

"The electrostatic force F_{E} between two point charges q_{1} and q_{2} is proportional to the product of the charges and inversely proportional to the square of the distance d that separates them, and has the direction of the line that joins them"  

Mathematically this law is written as:  

F_{E}= K\frac{q_{1}.q_{2}}{d^{2}}  

Where K is a proportionality constant.  

Now, if q_{1} and q_{2} have the same sign charge (both positive or both negative), a repulsive force will act on these charges.

5 0
3 years ago
The graph shows the motion of a car. Which segment shows that the car is slowing down? A, B, C, or D Graph:
shutvik [7]

Answer:

Segment c

Explanation:

5 0
3 years ago
Read 2 more answers
Why is 30% recommended as the minimum Michelson contrast?
forsale [732]

Answer:

Explained

Explanation:

Michelson contrast is used for patterns where the distribution of bright and dark segments is nearly equal.

It is given by:

m= \frac{I_{max}-I{min}}{I_{max}+I{min} }

where I_max = maximum illumination and I_min = minimum illumination

we know that

typically, I_min = 54% of I_max  (general standard)

or I_min = 0.54 I_max

putting this value in above equation to get m

this approximately corresponds to m = 0.3 or 30%

hence, 30% recommended as the minimum Michelson contrast

6 0
3 years ago
You charge an initially uncharged 89.9-mf capacitor through a 30.5-ω resistor by means of a 9.00-v battery having negligible int
blsea [12.9K]
<span>1) The differential equation that models the RC circuit is :

(d/dt)V_capacitor </span>+ (V_capacitor/RC)​ = (V_source/<span>RC)​​</span>

<span>Where the time constant of the circuit is defined by the product of R*C

Time constant = T = R*C = (</span>30.5 ohms) * (89.9-mf) = 2.742 s


2)
C<span>harge of the capacitor 1.57 time constants

1.57*(2.742) = 4.3048 s

The solution of the differential equation is

</span>V_capac (t) = (V_capac(0) - V_capac(∞<span>))e ^(-t /T)  +  </span>V_capac(∞)

Since the capacitor is initially uncharged V_capac(0) = 0

And the maximun Voltage the capacitor will have in this configuration is the voltage of the battery  V_capac(∞) = 9V 

This means,

V_capac (t) = (-9V)e ^(-t /T)  +  9V

The charge in a capacitor is defined as Q = C*V

Where C is the capacitance and V is the Voltage across

V_capac (4.3048 s) = (-9V)e ^(-4.3048 s /T)  +  9V

V_capac (4.3048 s) = (-9V)e ^(-4.3048 s /2.742 s)  +  9V

V_capac (4.3048 s) = (-9V)e ^(-4.3048 s /2.742 s)  +  9V = -1.87V +9V

V_capac (4.3048 s) = 7.1275 V

Q (4.3048 s)  = 89.9mF*(7.1275V) = 0.6407 C

3) The charge after a very long time refers to the maximum charge the capacitor will hold in this circuit. This occurs when the voltage accross its terminals is equal to the voltage of the battery = 9V

Q (∞)  = 89.9mF*(9V) = 0.8091 C
7 0
2 years ago
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