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Ch. 36 - The Special Theory of Relativity
Giancoli Douglas - Physics for Scientists and Engineers 5th edition
Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoGiancoli Douglas 5th editionCh. 36 - The Special Theory of RelativityProblema 83
Capitolo 35, Problema 83

Two protons, each having a speed of 0.945c in the laboratory, are moving toward each other. Determine (a) the momentum of each proton in the laboratory, (b) the total momentum of the two protons in the laboratory, and (c) the momentum of one proton as seen by the other proton.

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Identify the mass of a proton, which is a constant value, and the speed of each proton given as 0.945 times the speed of light (c).
Calculate the relativistic momentum for each proton using the formula p = \( \gamma mv \), where \( m \) is the rest mass of the proton, \( v \) is the velocity of the proton, and \( \gamma \) is the Lorentz factor calculated by \( \gamma = \frac{1}{\sqrt{1 - \left(\frac{v}{c}\right)^2}} \).
For part (b), determine the total momentum of the two protons in the laboratory. Since they are moving directly towards each other with equal speeds, their momenta are equal in magnitude but opposite in direction, leading to a total momentum of zero.
For part (c), calculate the momentum of one proton as seen by the other. Use the relativistic velocity addition formula to find the relative velocity (V) of one proton with respect to the other: \( V = \frac{2v}{1 + \left(\frac{v^2}{c^2}\right)} \).
Using the relative velocity (V) obtained from the previous step, calculate the momentum of one proton as seen by the other using the same relativistic momentum formula p = \( \gamma mv \), substituting V for v.

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Relativistic Momentum

In relativistic physics, momentum is defined as the product of an object's mass and its velocity, modified by the Lorentz factor, which accounts for the effects of traveling at speeds close to the speed of light. The formula for relativistic momentum is p = γmv, where γ (gamma) is the Lorentz factor, given by γ = 1 / √(1 - v²/c²). This concept is crucial for accurately calculating the momentum of particles moving at relativistic speeds.
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Lorentz Factor

The Lorentz factor (γ) is a key component in the theory of relativity, representing the factor by which time, length, and relativistic mass increase as an object approaches the speed of light. It is calculated using the formula γ = 1 / √(1 - v²/c²), where v is the object's velocity and c is the speed of light. Understanding the Lorentz factor is essential for determining how relativistic effects influence momentum and other physical quantities.
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Conservation of Momentum

The principle of conservation of momentum states that the total momentum of a closed system remains constant if no external forces act upon it. In the context of two protons colliding, this principle allows us to analyze their momenta before and after the interaction. It is fundamental for solving problems involving collisions and interactions in both classical and relativistic physics.
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