Basic relativity question (probably easy for everyone on here xD)

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In summary, a quasar moving away from Earth with a speed of 0.850C emits a proton that reaches Earth at a speed of 0.519C relative to Earth. To find the proton's speed relative to the quasar, the formula u = u' +v / (1 + u'v/c^2) can be used. However, the meaning of the symbols u, u', and v needs to be clarified in order to solve the equation correctly. The given attempt of 0.578C as the proton's speed relative to Earth is contradicted by the given information and does not make sense.
  • #1
jayjay713
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Homework Statement



a quasar is moving away from Earth with a speed 0f 0.850c. It emits a proton that eventually reaches Earth with a speed of 0.519c relative to the earth. How fast is the proton moving relative to the QUASAR.

The Attempt at a Solution



u = u' + v / 1 + u'(v) / c^2

u = 0.578c relative to earth.

How do I go about getting an answer relative to the object emitting the proton?

thanks for help. appreciate it
 
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  • #2
Your equation is kindof hard to read, since it has several division signs. And are u,u' and v the absolute values of the speeds?

Also, Is this homework? You should show your own working first, since we're only meant to help with homework.
 
  • #3
A quasar is moving AWAY from the Earth with a speed of 0.850C. Itemits a proton that eventually reaches the earth, and is traveling at a speed of 0.519C relative to the EARTH. how fast is the proton moving RELATIVE to the QUASAR?

my attempt: u = u' +v / (1 + u'v/c^2)
u = 0.578c RELATIVE to EARTH.

however, I am looking for the speed RELATIVE to the QUASAR. I do not know how to do that with that given formula!

any ideaS? thanks
 
  • #4
jayjay713 said:
A quasar is moving AWAY from the Earth with a speed of 0.850C. Itemits a proton that eventually reaches the earth, and is traveling at a speed of 0.519C relative to the EARTH. how fast is the proton moving RELATIVE to the QUASAR?

my attempt: u = u' +v / (1 + u'v/c^2)
u = 0.578c RELATIVE to EARTH.

however, I am looking for the speed RELATIVE to the QUASAR. I do not know how to do that with that given formula!

any ideaS? thanks

The equation is still hard to read, man. Does it mean:
[tex]u= \frac{u'+v}{1+ \frac{u' v}{c^2}}[/tex]
And you said that u=0.578c relative to earth, but that doesn't make sense, because you already know the speed of the proton and the quasar relative to earth.
I think you should start by defining what u, u' and v mean in your equation.
 
  • #5
i don't know what it means? it's on the formula sheet there is an example using it. all i want to know is the speed of the proton relative to the quasar...
QUASAR<-0.85c-<QUASAR "shoots" PROTON>0.519>PROTON <EARTH>
the velocities are relative to earth.

THERE! I DREW IT OUT :) Does that make sense?
 
  • #6
Yes, I already understood that bit. But I'm trying to help you through the question. Since you have the equation, you just need to work out what the symbols mean. Try to work it out from your formula sheet.
 
  • #7
jayjay713 said:
A quasar is moving AWAY from the Earth with a speed of 0.850C. Itemits a proton that eventually reaches the earth, and is traveling at a speed of 0.519C relative to the EARTH. how fast is the proton moving RELATIVE to the QUASAR?

my attempt: u = u' +v / (1 + u'v/c^2)
u = 0.578c RELATIVE to EARTH.
Do you see the contradiction between the two things in red? That's why BruceW said it didn't make sense.

In any case, how did you manage to come up with 0.578c? I don't get that when I plug in the numbers the way I assume you did.
 

1. What is basic relativity?

Basic relativity is a branch of physics that explains the relationships between space, time, and gravity. It was first developed by Albert Einstein in the early 20th century and has since been confirmed by numerous experiments and observations.

2. How does relativity affect our daily lives?

While relativity may seem like a complex and abstract concept, it actually has many practical applications in our daily lives. GPS technology, for example, relies on the principles of relativity to accurately determine our location on Earth. Relativity also plays a role in the functioning of satellite communications, nuclear power plants, and even in the design of modern airplanes.

3. What is the difference between special and general relativity?

Special relativity deals with the relationship between space and time in the absence of gravity, while general relativity includes the effects of gravity. Special relativity is based on the principle of the constancy of the speed of light, while general relativity introduces the concept of spacetime curvature due to the presence of massive objects.

4. How does relativity explain the phenomenon of time dilation?

According to relativity, time is not absolute but is instead relative to the observer's frame of reference. This means that time can appear to pass at different rates for different observers depending on their relative motion or the strength of gravity in their location. This phenomenon, known as time dilation, has been observed in experiments and is an important aspect of relativity.

5. Can relativity be reconciled with quantum mechanics?

While relativity and quantum mechanics are two of the most successful and well-tested theories in physics, they have not yet been fully reconciled. The two theories operate on different scales and have different mathematical frameworks, making it challenging to merge them into a single theory. However, many scientists continue to work towards a unified theory that can explain both the macroscopic world of relativity and the microscopic world of quantum mechanics.

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