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Dmitrij [34]
3 years ago
15

Suppose you observe two stars and you know they have the same luminosity. If one star is twice as far away as the other, the mor

e distant star will appear how many times fainter?
Physics
1 answer:
rosijanka [135]3 years ago
5 0

Answer:

The farther star will appear 4 times fainter than the star that is near to the observer.

Explanation:

Since it is given that the luminosity of the 2 stars is same thus they radiate the same energy per unit time

Consider a spherical wave front of energy 'E' that leaves both the stars (Both radiate 'E' as they have same luminosity)

This Energy is spread over the whole surface area of sphere Thus when the wave front is at a distance 'r' the energy per unit surface area is given by

e_{1}=\frac{E}{4\pi r^{2}}

For the star that is twice away from the earth the distance is '2r' thus we will receive an energy given by

e_{2}=\frac{E}{4\pi (2r)^{2}}=\frac{E}{8\pi r^{2}}=\frac{e_{1}}{4}

Hence we sense it as 4 times fainter than the nearer star.

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3. Our favorite nature explorer Steve Irwin is currenty warking with crocodiles in the Nile River. One of the big boy crocs gets
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K.E = 4800 Joules.

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5 0
3 years ago
PLEASE HELP ASAP!!!!
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Answer:12.5 W

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A particular electric car is supplied with 300 kJ of chemical energy by the battery. Of this, a total of 70.5 kJ of energy is wa
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Supplied energy=300kJ

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\\ \sf\longmapsto 300-70.5=229.5kJ

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\boxed{\sf Efficiency=\dfrac{Used\:Energy}{Supplied\:Energy}\times 100}

\\ \sf\longmapsto Efficiency=\dfrac{229.5}{300}\times 100

\\ \sf\longmapsto Efficiency=\dfrac{229.5}{3}

\\ \sf\longmapsto Efficiency=76.5\%

3 0
2 years ago
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