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Two particles are created in a high-energy accelerator and move off in opposite directions. The speed of one particle, as measured in the laboratory, is \(0.650 c,\) and the speed of each particle relative to the other is \(0.950 c\). What is the speed of the second particle, as measured in the laboratory?

Short Answer

Expert verified
The speed of the second particle, as measured in the laboratory, is -0.580c.

Step by step solution

01

- Understanding and labeling given values

Firstly, it's essential to understand and label the given values properly. Let's denote the speed of the first particle as measured in the laboratory as \(v_1 = 0.650c\). The speed of the particles relative to each other is given as \(v' = 0.950c\). The speed of the second particle, as measured in the laboratory, is unknown and will be labeled as \(v_2\). We must solve for \(v_2\).
02

- Setting up the Einstein's addition of velocities equation

The equation for Einstein's addition of velocities is given as \( v' = (v+u)/(1+(vu/c^2)) \). In our case, we need to express this in terms of \(v_2\), so our equation becomes \( v' = (v_1 + v_2) / (1 + v_1v_2/c^2) \).
03

- Substituting known values

Substitute the known values for \(v_1\) and \(v'\), the equation becomes \( 0.950c = (0.650c + v_2) / (1 + (0.650c)(v_2/c^2)) \). This equation must be solved for \(v_2\).
04

- Solving for \(v_2\)

Solving for \(v_2\) involves rearranging the equation, cross multiplying, and collecting terms. The result is a quadratic equation in \(v_2\), which can be solved by the quadratic formula \(v_2 = [-b±sqrt(b^2-4ac)] / (2a)\). After solving, we find that \(v_2 = -0.580c, 1.550c\). Since the speed cannot exceed the speed of light, we discard the second solution.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Velocity
Velocity is a fundamental concept in physics that describes how fast an object moves in a specific direction. Here, we're studying particles moving almost at the speed of light. In a high-energy accelerator, particles are propelled to extremely high speeds. To calculate their speed, measured in terms of the speed of light (denoted as \(c\)), we often deal with fractions and decimals, indicating how close they are to reaching \(c\).
Understanding velocity at near-light speeds helps us grasp Einstein's theories because regular arithmetic doesn't apply when you're moving almost as fast as light. Instead, we use Einstein's addition of velocities to account for relativistic effects, ensuring accuracy when measuring one particle's velocity relative to another.
Einstein's addition lets us combine these incredible speeds without exceeding the ultimate cosmic speed limit: the speed of light. The formula that accommodates for this is crucial in calculations, avoiding speeds over \(c\), which is impossible for anything with mass based on our current understanding of physics.
Relativity
Relativity is a cornerstone of modern physics introduced by Albert Einstein. It fundamentally alters how we understand space, time, and velocity, especially for objects moving at significant fractions of the speed of light. According to the theory of relativity, time and space are not absolute. Instead, their measurements depend on the observer's state of motion.
The exercise delves into the core of relativity by exploring how different observers measure different velocities when particles are moving at high speeds. It showcases the necessity of using Einstein's addition of velocities to correctly predict and measure these velocities.
Without relativity, measurements would incorrectly assume that speeds simply add up, potentially exceeding the speed of light. This theory prevents such discrepancies, showing that velocities near the speed of light behave differently than at lower speeds. In the context of the exercise, relativistic effects cause the calculated lab speed of the second particle to differ from our initial expectations if we used classical calculations.
High-energy accelerator
A high-energy accelerator is a scientific instrument that propels particles to incredibly high velocities close to the speed of light. These accelerators are crucial for research in particle physics, allowing scientists to explore fundamental components of matter and the forces that govern them.
The exercise mentioned occurs in such an environment, where two particles are accelerated in opposite directions. Because these speeds are so close to light speed, classic physics is replaced by relativistic equations, like Einstein's addition of velocities.
High-energy accelerators create conditions similar to those shortly after the Big Bang, making them essential for testing theoretical predictions about particle interactions and generating new forms of matter.
  • Allows scientists to break particles into their smallest constituents.
  • Enables the exploration of new physics beyond the standard model.
  • Helps simulate extreme conditions and test theoretical models.
Ultimately, these devices provide the essential experimental testbed for theories like relativity.
Speed of light
The speed of light, denoted as \(c\), is approximately 299,792,458 meters per second. This speed is a universal constant in the universe and forms the backbone of the theory of relativity. Nothing with mass can reach or exceed \(c\) in a vacuum. Thus, it's the ultimate speed limit.
In our exercise, both particles reach speeds expressed as a fraction of \(c\). Understanding these speeds in the lab frame demands considering relativistic effects as described by Einstein since traditional velocity addition would be inaccurate.
Einstein's work showed that as an object moves closer to the speed of light, its mass effectively becomes infinite, requiring infinite energy to continue accelerating. This makes reaching \(c\) impossible for massive objects, which is why high-energy physics often speaks about fractions of \(c\). By adhering to these principles, researchers ensure that their calculations respect the cosmic speed limit, preserving the laws of physics.

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Most popular questions from this chapter

As a research scientist at a linear accelerator, you are studying an unstable particle. You measure its mean lifetime \(\Delta t\) as a function of the particle's speed relative to your laboratory equipment. You record the speed of the particle \(u\) as a fraction of the speed of light in vacuum \(c .\) The table gives the results of your measurements. $$ \begin{array}{l|lllllll} u / c & 0.70 & 0.80 & 0.85 & 0.88 & 0.90 & 0.92 & 0.94 \\ \hline \Delta t\left(10^{-8} \mathrm{~s}\right) & 3.57 & 4.41 & 5.02 & 5.47 & 6.05 & 6.58 & 7.62 \end{array} $$ (a) Your team leader suggests that if you plot your data as \((\Delta t)^{2}\) versus \(\left(1-u^{2} / c^{2}\right)^{-1},\) the data points will be fit well by a straight line. Construct this graph and verify the team leader's prediction. Use the best-fit straight line to your data to calculate the mean lifetime of the particle in its rest frame. (b) What is the speed of the particle relative to your lab equipment (expressed as \(u / c\) ) if the lifetime that you measure is four times its rest-frame lifetime?

In a particle accelerator a proton moves at constant speed \(0.750 c\) in a circle of radius \(628 \mathrm{~m} .\) What is the net force on the proton?

Physicists and engineers from around the world came together to build the largest accelerator in the world, the Large Hadron Collider (LHC) at the CERN Laboratory in Geneva, Switzerland. The machine accelerates protons to high kinetic energies in an underground ring \(27 \mathrm{~km}\) in circumference. (a) What is the speed \(v\) of a proton in the \(\mathrm{LHC}\) if the proton's kinetic energy is \(7.0 \mathrm{TeV} ?\) (Because \(v\) is very close to \(c,\) write \(v=(1-\Delta) c\) and give your answer in terms of \(\Delta .\) ) (b) Find the relativistic mass, \(m_{\text {rel }}\), of the accelerated proton in terms of its rest mass.

A particle zips by us with a Lorentz factor of \(1.12 .\) Then another particle zips by us moving at twice the speed of the first particle. (a) What is the Lorentz factor of the second particle? (b) If the particles were moving with a speed much less than \(c,\) the magnitude of the momentum of the second particle would be twice that of the first. However, what is the ratio of the magnitudes of momentum for these relativistic particles?

A spaceship flies past Mars with a speed of \(0.985 c\) relative to the surface of the planet. When the spaceship is directly overhead, a signal light on the Martian surface blinks on and then off. An observer on Mars measures that the signal light was on for \(75.0 \mu\) s. (a) Does the observer on Mars or the pilot on the spaceship measure the proper time? (b) What is the duration of the light pulse measured by the pilot of the spaceship?

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