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3 years ago

Which of the following statements is an accurate description of vibrations?

2 answers:

6 0

<span>So we want to know what statement is an accurate description of vibrations. So humans can hear sound frequencies from 20-20000 Hz. Below 20 Hz is infra sound and above 20000 Hz is ultra sound. Humans cant hear both infra sound and ultra sound so the correct answer is A.</span>

Daniel [21]3 years ago

6 0

Infrasonic and ultrasonic vibrations can’t be heard by humans because they’re outside of the range of frequencies that can be detected. Infrasonic vibrations have a lower frequency than can be heard by the human ear; ultrasonic vibrations have a higher frequency than can be heard by the human ear. Infrasonic vibrations can be felt if the amplitude is great enough. Ultrasonic vibrations are utilized in sonar equipment and in applications to detect flaws in steel castings and to remove grease or foreign material from machine-part surfaces.

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(a) What is the cost of heating a hot tub containing 1440 kg of water from 10.0°C to 40.0°C, assuming 75.0% efficiency to take h

BaLLatris [955]

Answer:

a) $E = 6.024\,USD$ , For m kilograms, it is 4184m J., 3600000 joules, b) $i = 88.200\,A$

Explanation:

a) The amount of heat needed to warm water is given by the following expression:

$Q_{needed} = m_{w}\cdot c_{w}\cdot (T_{f}-T_{i})$

Where:

$m_{w}$ - Mass of water, measured in kilograms.

$c_{w}$ - Specific heat of water, measured in $\frac{J}{kg\cdot ^{\circ}C}$ .

$T_{f}$ , $T_{i}$ - Initial and final temperatures, measured in $^{\circ}C$ .

Then,

$Q_{needed} = (1440\,kg)\cdot \left(4184\,\frac{J}{kg\cdot ^{\circ}C} \right)\cdot (40^{\circ}C - 10^{\circ}C)$

$Q_{needed} = 180748800\,J$

The energy needed in kilowatt-hours is:

$Q_{needed} = 180748800\,J\times \left(\frac{1}{3600000}\,\frac{kWh}{J} \right)$

$Q_{needed} = 50.208\,kWh$

The electric energy required to heat up the water is:

$E = \frac{50.208\,kWh}{0.75}$

$E = 66.944\,kWh$

Lastly, the cost of heating a hot tub is: (USD - US dollars)

$E = (66.944\,kWh)\cdot \left(0.09\,\frac{USD}{kWh} \right)$

$E = 6.024\,USD$

The heat needed to raise the temperature a degree of a kilogram of water is 4184 J. For m kilograms, it is 4184m J. Besides, a kilowatt-hour is equal to 3600000 joules.

b) The current required for the electric heater is:

$i = \frac{Q_{needed}}{\eta \cdot \Delta V \cdot \Delta t}$

$i = \frac{180748800\,J}{0.75\cdot (220\,V)\cdot (3.45\,h)\cdot \left(3600\,\frac{s}{h} \right)}$

$i = 88.200\,A$

7 0

3 years ago

QUICK PLEASE! WILL GIVE BRAINLIEST!

Crank

Answer:

hi!

Explanation:

i think the answer is x=0m , y=0,55m

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when an electric current is flowing through a wire which of the following is also produced energy domain field force

qaws [65]

When an electric current is flowing through a wire, there is a magnetic <em>field</em> produced. The lines of magnetic force are circles around the wire.

4 0

3 years ago

What is the percentage of the incoming solar radiation from the top of the atmosphere the gets reflected right back out into spa

san4es73 [151]

Answer: We can define the solar constant as a measure of the luminous flux density.

Explanation:

The solar constant or solar constant is the amount of energy radiated at the upper limit of the Earth's atmosphere per unit time perpendicular to the unit surface, at the Earth's mean distance from the sun. Amounts to 1367.7 W / m² ± 6 W / m². The sun's constant includes all kinds of electromagnetic radiation, not just visible light. The average value is 1,368 kW / m2 and changes slightly with solar cycles. The amount of these constant changes over one year and has different benefits.

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3 years ago

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mash [69]

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