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Finger [1]
3 years ago
9

A 21.7kg child descends a slide 3.5 m high and reaches the bottom with a speed of 2.2m/s. How much thermal energy due to frictio

n was generated in this process?
Physics
1 answer:
nadya68 [22]3 years ago
5 0

Answer:

Subtract the kinetic energy at the bottom from the potential energy loss. The remainder becomes frictional heat.

Potential energy loss:

M g H = 21.7*9.81*3.5 = 745.1 J

Kinetic energy at bottom of slide:

= (1/2) M v^2 = 52.5 J

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An ideal photo-diode of unit quantum efficiency, at room temperature, is illuminated with 8 mW of radiation at 0.65 µm wavelengt
nadya68 [22]

Answer:

I = 4.189 mA    V = 0.338 V

Explanation:

In order to do this, we need to apply the following expression:

I = Is[exp^(qV/kT) - 1]   (1)

However, as the junction of the diode is illuminated, the above expression changes to:

I = Iopt + Is[exp^(qV/kT) - 1]   (2)

Now, as the shunt resistance becomes infinite while the current becomes zero, we can say that the leakage current is small, and so:

I ≅ Iopt

Therefore:

I ≅ I₀Aλq / hc  (3)

Where:

I₀A = Area of diode (radiation)

λ: wavelength

q: electron charge (1.6x10⁻¹⁹ C)

h: Planck constant (6.62x10⁻³⁴ m² kg/s)

c: speed of light (3x10⁸ m/s)

Replacing all these values, we can get the current:

I = (8x10⁻³) * (0.65x10⁻⁶) * (1.6x10⁻¹⁹) / (6.62x10⁻³⁴) * (3x10⁸)

I = 4.189x10⁻³ A or 4.189 mA

Now that we have the current, we just need to replace this value into the expression (2) and solve for the voltage:

I = Is[exp^(qV/kT) - 1]

k: boltzman constant (1.38x10⁻²³ J/K)

4.189x10⁻³ = 9x10⁻⁹ [exp(1.6x10⁻¹⁹ V / 1.38x10⁻²³ * 300) - 1]

4.189x10⁻³ / 9x10⁻⁹ = [exp(38.65V) - 1]

465,444.44 + 1  = exp(38.65V)

ln(465,445.44) = 38.65V

13.0508 = 38.65V

V = 0.338 V

6 0
3 years ago
Calculate the magnitude of the angular momentum of the earth due its daily rotation about its own axis
ioda
L=Iw
I_{earth} =  \frac{2}{5} r^{2}m= \frac{2}{5} (6371000^2m)(5.97*10^{24}kg)=9.71*10^ {37}
L_{earth}=Iw=(9.71*10^ {37})(7.27*10^{-5})=7.07*10^{33}<span>[/tex]</span>

7 0
3 years ago
A simple harmonic wave of wavelength 18.7 cm and amplitude 2.34 cm is propagating along a string in the negative x-direction at
storchak [24]

Answer

given,

wavelength = λ = 18.7 cm

                    = 0.187 m

amplitude , A = 2.34 cm

v = 0.38 m/s

A)  angular frequency = ?

     f = \dfrac{v}{\lambda}

     f = \dfrac{0.38}{0.187}

     f =2.03\ Hz

angular frequency ,

ω = 2π f

ω = 2π x 2.03

ω = 12.75 rad/s

B) the wave number ,

      K = \dfrac{2\pi}{\lambda}

     K= \dfrac{2\pi}{0.187}

    K =33.59\ m^{-1}

C)

as the wave is propagating in -x direction, the sign is positive between x and t

y ( x ,t) = A sin(k  x - ω t)

y ( x ,t) = 2.34  x  sin(33.59 x - 12.75 t)

4 0
3 years ago
As the spaceship travels upward in the sky, some of its kinetic energy will be lost to the universe due to ?
GaryK [48]

Answer:

Friction !!!

Explanation:

6 0
3 years ago
A student read his right ear against his desk while Teacher talks loudly on the desk and can hear the tapping sound only through
sladkih [1.3K]

Answer:

The student hears the wave that is transmitted by the desk

Explanation:

Mechanical waves need a material medium to be able to be transmitted, in the case of sound waves, one of the most common media is air, but it is also transmitted in other media in this case, stationery is transmitted.

The student hears the wave that is transmitted by the desk

The speed of the wave is proportional to the density of the material, so the wave that the student hears arrives much faster through the desk than through the air

6 0
3 years ago
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