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Vikentia [17]
3 years ago
7

An empty office chair is at rest on a floor. Consider the following forces:. 1. A downward force due to gravity;. 2. An upward forc

e exerted by the floor; and. 3. A net downward force exerted by the air. Which force(s) act on the office chair?. 1. None of the forces act on the chair since. it is at rest. 2. All three forces. 3. 1 only. 4. 1 and 2 only. 5. 2 and 3 only.
Physics
1 answer:
Ghella [55]3 years ago
7 0
The answer is:

<span> 4. 1 and 2 only.</span>
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What is the difference between flashing point, boiling point and melting point​
sp2606 [1]
<h3><u>Answer and explanation;</u></h3>
  • <u>Melting point</u> is defined as the temperature at which solid and liquid phases are in equilibrium. It is the temperature at which a solid changes state from solid to liquid at atmospheric pressure.
  • <u>Boiling poin</u>t is the temperature at which the vapour pressure of a liquid is equal to the external pressure. It is the temperature at which a substance changes from a liquid into a gas.
  • <u>The flash point </u>of a flammable liquid or volatile liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperature the vapor may cease to burn when the source of ignition is removed.
8 0
3 years ago
Read 2 more answers
Calculate the wavelength of each frequency of electromagnetic radiation: a. 100.2 MHz (typical frequency for FM radio broadcasti
Natalka [10]

Answer:

a). 100.2 MHz (typical frequency for FM radio broadcasting)

The wavelength of a frequency of 100.2 Mhz is 2.99m.

b. 1070 kHz (typical frequency for AM radio broadcasting) (assume four significant figures)

The wavelength of a frequency of 1070 khz is 280.3 m.

c. 835.6 MHz (common frequency used for cell phone communication)

The wavelength of a frequency of 835.6 Mhz is 0.35m.

Explanation:

The wavelength can be determined by the following equation:

c = \lambda \cdot \nu  (1)

Where c is the speed of light, \lambda is the wavelength and \nu is the frequency.  

Notice that since it is electromagnetic radiation, equation 1 can be used. Remember that light propagates in the form of an electromagnetic wave.

<em>a). 100.2 MHz (typical frequency for FM radio broadcasting)</em>

Then, \lambda can be isolated from equation 1:

\lambda = \frac{c}{\nu} (2)

since the value of c is 3x10^{8}m/s. It is necessary to express the frequency in units of hertz.

\nu = 100.2 MHz . \frac{1x10^{6}Hz}{1MHz} ⇒ 100200000Hz

But 1Hz = s^{-1}

\nu = 100200000s^{-1}

Finally, equation 2 can be used:

\lambda = \frac{3x10^{8}m/s}{100200000s^{-1}}

\lambda = 2.99 m

Hence, the wavelength of a frequency of 100.2 Mhz is 2.99m.

<em>b. 1070 kHz (typical frequency for AM radio broadcasting) (assume four significant figures)</em>

<em> </em>

\nu = 1070kHz . \frac{1000Hz}{1kHz} ⇒ 1070000Hz

But  1Hz = s^{-1}

\nu = 1070000s^{-1}

Finally, equation 2 can be used:

\lambda = \frac{3x10^{8}m/s}{1070000s^{-1}}

\lambda = 280.3 m

Hence, the wavelength of a frequency of 1070 khz is 280.3 m.

<em>c. 835.6 MHz (common frequency used for cell phone communication) </em>

\nu = 835.6MHz . \frac{1x10^{6}Hz}{1MHz} ⇒ 835600000Hz

But  1Hz = s^{-1}

\nu = 835600000s^{-1}

Finally, equation 2 can be used:

\lambda = \frac{3x10^{8}m/s}{835600000s^{-1}}

\lambda = 0.35 m

Hence, the wavelength of a frequency of 835.6 Mhz is 0.35m.

6 0
3 years ago
Compared to water, most metals have low specific heats.<br> true<br> or<br> false
Alchen [17]
Yes that's a true statement. That's why grandmother put a hot water bottle to warm up her bed, and not a hot bar of steel or lead.
8 0
3 years ago
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Which quantity below is a derived quantity?
Reil [10]

By definition, the speed of an object is given by:

v = \frac{dr}{dt}

Where,

dr/dt: derived from the position with respect to time

Therefore, speed has units of length over units of time.

Thus, speed is a derived quantity, since it depends on the value of two other quantities.

Answer:

a derived quantity is:

C. Speed

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3 years ago
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If an object has 180 J of PE and a mass of .5kg, what is its height?
Nonamiya [84]
PE=mgh
180=0.5*10*h
180=5h
h=180/5=36 m
7 0
3 years ago
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