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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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The specific weight of sea water is 10.1 kN/m^3. Convert to lbs/in^3.
Viktor [21]

Answer:

0.03719 lbs/in³

Explanation:

Specific weight is given by multiplying the density of an object to the acceleration due to gravity.

\gamma =\rho g\\\Rightarrow \rho=\frac{gamma}{g}\\\Rightarrow \rho=\frac{10.1\times 10^3}{9.81}\\\Rightarrow \rho=1029.562\ kg/m^3

1\ kg=2.20462\ lb

1\ m=39.3701\ in

\\\Rightarrow 1029.562\ kg/m^3=\frac{1029.562\times 2.20462}{39.3701^3}=0.03719\ lbs/in^3

So,

10.1\ kN/m^3=0.03719\ lbs/in^3

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A speeder is pulling directly away and increasing his distance from a police car that is moving at 24 m/s with respect to the gr
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A pulley system lifts a 1345 n weight a distance of 0.975m. Paul pulls the rope a distance of 3.90m, exerting a force of 375N. A
Rashid [163]

A. IMA: 4

The Ideal Mechanical Advantage (IMA) is given by:

IMA = \frac{d_i}{d_o}

where

d_i is the input distance

d_o is the output distance

For the pulley system in this problem, d_i = 3.90 m and d_o = 0.975 m, so the IMA is

IMA=\frac{3.90 m}{0.975 m}=4


B. MA: 3.59

The actual mechanical advantage (AMA), or simply the Mechanical Advantage (MA), is given by

MA=\frac{F_o}{F_i}

where F_o is the output force and F_i is the input force. For the pulley system in this problem, F_i = 375 N and F_o = 1345 N, so the MA is

MA=\frac{1345 N}{375 N}=3.59


C. Efficiency: 89.8 %

The efficiency of a machine is equal to the ratio between the MA and the AMA:

\eta = \frac{MA}{AMA} \cdot 100

Therefore, in this case,

\eta=\frac{3.59}{4}\cdot 100=0.898=89.8 \%

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