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3 years ago

Why does the frequency of a siren get higher as an ambulance using that siren gets closer?

2 answers:

7 0

The answer is D. As the ambulance gets closer, the sound waves are compressed relative to the person; so the frequency increases.

yarga [219]3 years ago

7 0

I would say that the answer is D)

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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

Describe how work is done by a skater pulling in her arms during a spin. In particular, identify the force she exerts on each ar

liberstina [14]

Answer:

∑ τ =0, L₀ = $L_{f}$

Explanation:

In a circular turning movement, when the arms are extended and then contracted in two possibilities:

- They are lowered the force of gravity is what pulls them, the tension of the muscle becomes zero to allow this movement.

In this movement the force is vertical(gravity) and the movement of the center of mass of each arm is vertical, so that the work is the weight value of the arm by the distance traveled by the center of mass.

- Another possibility is that the arms have stuck to the body, in this case the person's muscles perform the force, this force is horizontal and the displacement is the horizontal of the center of mass of the arms from the extended position to the contracted

In these movements the torque of the external force is equal for each arm, but in the opposite direction, so they are canceled where a net torque of zero, this causes the angular momentum to be preserved, which changes is the moment of inertia of the system and therefore you must also change the angular velocity to keep your product constant

∑ τ =0

L₀ = $L_{f}$

I₀ w₀ = I w

4 0

3 years ago

The 59 converted into binary is _____.<br> How do we convert number to binary?

Viefleur [7K]

Answer:

111011

Explanation:

59/2 = 29, remainder is 1

29/2 = 14, remainder is 1

14/2 = 7, remainder is 0

7/2 = 3, remainder is 1

3/2 = 1, remainder is 1

1/2 = 0, remainder is 1

8 0

3 years ago

A combination of two identical resistors connected in series has an equivalent resistance of 12. ohms. What is the equivalent re

SIZIF [17.4K]

Answer:

R1 + R2 = R = 12 for resistors in series - so R1 = R2 if they are identical

2 R1 = 12 and R1 = R2 = 6 ohms

1 / R = 1 / R1 + 1 / R2 for resistors in parallel

R = R1 * R2 / (R1 + R2) = 6 * 6 / (6 + 6) = 3

The equivalent resistance would be 3 ohms if connected in parallel

7 0

2 years ago

50 POINTS

strojnjashka [21]

Answer: A Answers. Assuming that the terminal velocity doesn't change during the fall, then the kinetic energy would remain constant. However the terminal velocity decreases during the fall since the air becomes denser at lower altitudes.

Explanation:

What happens to the KE of an object when it slows down and heats up? - Quora. The kinetic energy goes down and the loss of the kinetic energy is through the production of heat energy. In real world this is due to friction, or an opposing force that decelerates the object, or a combination of both.

8 0

3 years ago

Read 2 more answers