5. What's the temperature -10°C in kelvins?

Suppose astronomers discover a radio message from a civilization whose planet orbits a star 35 light-years away. Their message e

Grace [21]

Answer:

The duration is $T =72 \ years /tex]Explanation:From the question we are told that The distance is [tex]D = 35 \ light-years = 35 * 9.46 *10^{15} = 3.311 *10^{17} \ m$

Generally the time it would take for the message to get the the other civilization is mathematically represented as

$t = \frac{D}{c}$

Here c is the speed of light with the value $c = 3.08 *10^{8} \ m/s$

=> $t = \frac{3.311 *10^{17} }{3.08 *10^{8}}$

=> $t = 1.075 *10^9 \ s$

converting to years

$t = 1.075 *10^9 * 3.17 *10^{-8}$

$t = 34 \ years$

Now the total time taken is mathematically represented as

$T = 2* t + 2 + 2$

=> $T = 2* 34 + 2 + 2$

=> [tex]T =72 \ years /tex]

4 0

3 years ago

Which of the following means that an image is real?

DochEvi [55]

To declare an image is real you would call it “authentic”

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3 years ago

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1. Which of the following statements best describes matter?

Rashid [163]

Answer:

Matter is anything that has mass

Explanation:

The word "matter" refers to anything that has mass, either organic or inorganic. Matter is made up of atoms, which consists of a nucleus (made up of protons, positively charged, and neutrons, electrically neutron) and electrons which revolve around the nucleus.

The number of protons in the atom determine the element: there are more than 100 different elements in nature, with different properties depending on the number of electrons they have.

Matter can be in three different states also:

- solid: the atoms are tightly bond to each other, so they cannot move

- liquids: atoms are not bond to each other, so they can slide past each other, but still they have some intermolecular forces that keep them close to each other

- gas: atoms are free to move, as there are no forces that keep them close to each other

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3 years ago

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A body which has surface area 5cm² and temperature of 727°C radiates 300J of energy in one minute. Calculate it's emissivity giv

cestrela7 [59]

<h2>Answer: 0.17</h2>

Explanation:

The Stefan-Boltzmann law establishes that a black body (an ideal body that absorbs or emits all the radiation that incides on it) "emits thermal radiation with a total hemispheric emissive power proportional to the fourth power of its temperature":

$P=\sigma A T^{4}$ (1)

Where:

$P=300J/min=5J/s=5W$ is the energy radiated by a blackbody radiator per second, per unit area (in Watts). Knowing $1W=\frac{1Joule}{second}=1\frac{J}{s}$

$\sigma=5.6703(10)^{-8}\frac{W}{m^{2} K^{4}}$ is the Stefan-Boltzmann's constant.

$A=5cm^{2}=0.0005m^{2}$ is the Surface area of the body

$T=727\°C=1000.15K$ is the effective temperature of the body (its surface absolute temperature) in Kelvin.

However, there is no ideal black body (ideal radiator) although the radiation of stars like our Sun is quite close. So, in the case of this body, we will use the Stefan-Boltzmann law for real radiator bodies:

$P=\sigma A \epsilon T^{4}$ (2)