# [Relativity] Energy and momentum question

## Homework Statement

Write down a relation between the total relativistic energy, mass and momentum of a
particle. An antiproton has a total energy of 5.00 GeV. Calculate its momentum and its
speed.

## Homework Equations

E = γmc^2
E = (cp)^2 +(mc^2)^2
p = γmv

## The Attempt at a Solution

I've tried subbing everything in and playing around with the algebra but I cant get an expression entirely in terms of v or p.
Also how do you get the proper math equations on here? Are the tags [itex]?

Last edited:

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Dick
Homework Helper

## Homework Statement

Write down a relation between the total relativistic energy, mass and momentum of a
particle. An antiproton has a total energy of 5.00 GeV. Calculate its momentum and its
speed.

## Homework Equations

E = γmc^2
E = (cp)^2 +(mc^2)^2
p = γmv

## The Attempt at a Solution

I've tried subbing everything in and playing around with the algebra but I cant get an expression entirely in terms of v or p.
Also how do you get the proper math equations on here? Are the tags [itex]?
Here's a TeX tutorial. https://www.physicsforums.com/showpost.php?p=3977517&postcount=3 Try just using the second equation. You know E and you can look up the mass of the proton. That will get you p.

you can look up the mass of the proton
Sorry I should have said, this is a question from an exam a few years ago and it doesn't mention the mass of the proton anywhere in the entire paper. Is there a way to get the answer without knowing m?
Cheers for the tutorial!

Dick
Homework Helper
Sorry I should have said, this is a question from an exam a few years ago and it doesn't mention the mass of the proton anywhere in the entire paper. Is there a way to get the answer without knowing m?
Cheers for the tutorial!
No, you need to know something else besides just the energy.

jtbell
Mentor
Try just using the second equation.
And make that E^2, not E, on the left-hand side. Dick
And make that E^2, not E, on the left-hand side. 