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Sergio [31]
3 years ago
6

Which statement correctly describes variable stars?

Physics
1 answer:
Kryger [21]3 years ago
5 0

Answer:

D)

Explanation:

The Period-Luminosity relationship tells us that luminosity increases with the period, and of course the more luminosity a star has the more far away they can be seen, so from this we know that:

A) False since lower luminosities can be observed when they are close.

B) False since longer periods means higher luminosities

C) False since lower luminosities can be observed when they are close.

D) True: Variable stars with shorter periods have lower luminosities, so they can only be observed when they are close.

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Why is friction useful between your feet and the ground?
mixer [17]

Answer:

It allows you to walk faster.

Explanation:  

It is the same force that allows you to accelerate forward when you run. Your planted foot can grip the ground and push backward, which causes the ground to push forward on your foot. We call this grip type of friction, where the surfaces are prevented from slipping across each other, a static frictional force.

3 0
2 years ago
Read 2 more answers
Determine W (or fuel energy) required to launch a satellite of mass m at rest from a launching pad placed at the surface earth,
jeka57 [31]

Answer:

5. 9GmM/(10R)

Explanation:

m is the mass of the satellite

M is the mass of the earth

W is the energy required to launch the satellite

Energy at earth surface = Potential energy (PE) + W

W = Energy at earth surface - Potential energy (PE)

But PE = -\frac{GMm}{R}

Therefore: W = Energy at earth surface - \frac{GMm}{R}

Energy at earth surface (E) at an altitude of 5R = -\frac{GMm}{5r} +\frac{1}{2}mV^2

But V=\sqrt{\frac{GM}{5R} }

Therefore: E=-\frac{GMm}{5R}+\frac{1}{2}m(\sqrt{\frac{GM}{5R} } )^2=  -\frac{GMm}{5R}+\frac{GMm}{10R}  = -\frac{GMm}{10R}

W = E - PE

W=-\frac{GMm}{10R}-(-\frac{GMm}{R})=-\frac{GMm}{10R}+\frac{GMm}{R}=\frac{9GMm}{10R} \\W=\frac{9GMm}{10R}

7 0
3 years ago
How would you go about separating the components of a mixture of sand, gravel, salt and iron filings
larisa86 [58]

Pour the entire components into water.

First the iron filings can be separated using a magnet as iron is a magnetic element.

By pouring the mixture into water, it allows the salt to dissolve in the water, while the sand will not.

Next we can run this solution through a filtration device to separate the sand from the water.

Now all that's left is to let the water evaporate so that the salt will be exposed that dissolved into the water.

4 0
3 years ago
1. A sample of gas has a constant temperature and number of particles. As the volume of the gas sample is increased, the pressur
AURORKA [14]

Answer:

1.C

2.C

3.C

Explanation:

hope its help hehe:(

4 0
2 years ago
An elevator was a full mass of 2400 kg has a power rating on 16.5 horsepower how much time will it take the elevator to lift a f
ehidna [41]
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