Solve Relativistic Momentum PROBLEM - Extra Factor of u Explained

In summary, the conversation was about a problem set in SR and a mistake in the worked example. The proper momentum of the second particle was incorrectly calculated due to a misunderstanding of its definition. The correct definition includes an additional factor of velocity.
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meriadoc
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PROBLEM SOLVED - the worked example I was referring too was wrong :/
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Hello, I've been stuck on a question in one of my SR problem sets for some time now, and managed to find a worked solution to a similar problem online. I've attached an image of the problem (the missing text just says that two particles of equal mass are accelerated to a speed u).

It begins by showing that in frame S, both particles have the same energy, which is

[itex]E = \gamma m u[/itex]

It then uses the 4-momentum transformations for the second particle (the one that is moving in both frames), noting that

[itex](p^0)' = \gamma (p^0 - \frac{v}{c} (p^1)')[/itex]

But then it goes on to define [itex]p^1[/itex] as

[itex]p^1 = \gamma m u (-u)[/itex]

This is where I made the mistake in my working, I used

[itex]p^1 = \gamma m (-u)[/itex]

I don't understand why the proper momentum of the second particle has an additional factor of u associated with it. Any explanation would be greatly appreciated.

Cheers.
 

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Related to Solve Relativistic Momentum PROBLEM - Extra Factor of u Explained

What is relativistic momentum?

Relativistic momentum is a concept in physics that takes into account the effects of special relativity on the momentum of an object. It is given by the formula p = mu, where m is the mass of the object and u is its velocity.

What is the extra factor of u in the relativistic momentum formula?

The extra factor of u in the relativistic momentum formula accounts for the increase in an object's mass as it approaches the speed of light. This is known as relativistic mass and it causes the momentum to increase at high velocities.

How is relativistic momentum different from classical momentum?

Relativistic momentum takes into account the effects of special relativity, such as time dilation and length contraction, on an object's mass and velocity. In contrast, classical momentum only considers an object's mass and velocity in a non-relativistic context.

Why is it important to use relativistic momentum in certain situations?

Relativistic momentum is important to use in certain situations, particularly when dealing with objects moving at high speeds, such as particles in a particle accelerator. It provides a more accurate measurement of an object's momentum and allows for better predictions of its behavior.

How is relativistic momentum used in practical applications?

Relativistic momentum is used in a variety of practical applications, including in particle accelerators, space travel, and nuclear reactions. It is also important in understanding the behavior of subatomic particles and in the development of modern physics theories and models.

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