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4 years ago

Why does the presence of redshift in spectra of galaxies support an understanding of an expanding universe?

Physics

1 answer:

xenn [34]4 years ago

7 0

Explanation:

Doppler's Effect: If a source is moving towards the observer the frequency of the waves emitted by the source will increase( wavelength will decrease). If the source is moving away from the observer the frequency of the waves emitted by the source will decrease( wavelength will increase). The best example of this is the changing frequency of siren of an ambulance as it moves towards us and then away from us.

The same phenomenon can be observed in celestial objects. When the object will move towards us the wavelength will decrease thus the spectrum will be shifted towards the blue part. This is known as blue shift.

If the object moves away from us the wavelength will increase and thus the spectrum will be shifted towards red part. This is know as Red-shift. This is because red has longer wavelength (620 - 750nm) than blue (450-495nm)

Thus if a galaxy shows us red-shifted spectra it means that it is moving away from us. we have observed this phenomenon in various galaxies thus supporting the expanding universe theory.

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Consider the following statements about Newton's 2nd law in general. Select all of the statements that are true. Note, there may

Art [367]

Answer:

1. True

2. False

3. True

Explanation:

Newton's 2nd law states that the net force exerted on an object is equal to the product between the mass of the object and its acceleration:

$\sum F = ma$ (1)

where

$\sum F$ is the net force on the object

m is its mass

a is the acceleration

Furthermore, we know that acceleration is defined as the rate of change of velocity:

$a = \frac{dv}{dt}$

So let's now analyize the three statements:

1. A net force causes velocity to change: TRUE. Net force (means non-zero) causes a non-zero acceleration, which means that the velocity of the object must change.

2. If an object has a velocity, then we can conclude that there is a net force on the object: FALSE. The fact that the object has a velocity does not imply anything about its acceleration: in fact, if its velocity is constant, then its acceleration is zero, which would mean that the net force on the object is zero. So this statement is not necessarly true.

3. Accelerations are caused by the presence of a net force: TRUE. This is directly implied by eq.(1): the presence of the net force results in the object having a non-zero acceleration.

8 0

3 years ago

What is the definition of energy

natita [175]

Energy (in Physics) is the ability to do work.

5 0

3 years ago

How long (in seconds) does it take a car accelerating at 3.1 m/s2 to go from rest<br> to 51 m/s?

Nesterboy [21]

Answer:

t = 16.5s

Explanation:

Given parameters:

Acceleration = 3.1m/s²

Initial velocity = 0m/s

Final velocity = 51m/s

Unknown:

Time taken = ?

Solution:

To solve this problem we need to reiterate that acceleration is the rate of change of velocity with time.

So;

Acceleration = $\frac{v - u }{t}$

v is the final velocity

u is the initial velocity

t is the time taken

So;

3.1 = $\frac{51 - 0}{t}$

3.1t = 51

t = 16.5s

8 0

3 years ago

when an object falls, eventually the force of air resistance (drag) = the force of gravity. This is called ____

jarptica [38.1K]

Terminal velocity dkdkmfocmdpdmfpfmfl

4 0

3 years ago

How do I solve for the maximum speed and height given those accelerations? (please give the formula so I can solve these types o

Sphinxa [80]

It depends on how you want to solve it you can solve it in many different meathods:$

5 0

2 years ago