/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 34 You are driving down a two-lane ... [FREE SOLUTION] | 91Ó°ÊÓ

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You are driving down a two-lane country road, and a truck in the opposite lane is traveling toward you. Suppose that the speed of light in a vacuum is \(c=65 \mathrm{m} / \mathrm{s} .\) Determine the speed of the truck relative to you when (a) your speed is \(25 \mathrm{m} / \mathrm{s}\) and the truck's speed is \(35 \mathrm{m} / \mathrm{s}\) and \((\mathrm{b})\) your speed is \(5.0 \mathrm{m} / \mathrm{s}\) and the truck's speed is \(55 \mathrm{m} / \mathrm{s} .\) The speeds given in parts (a) and (b) are relative to the ground.

Short Answer

Expert verified
(a) 49.71 m/s, (b) 56.34 m/s.

Step by step solution

01

Identify the Relativistic Velocity Addition Formula

When dealing with velocities in relativistic physics (close to the speed of light), we use the relativistic velocity addition formula: \[ v_{rel} = \frac{v_1 + v_2}{1 + \frac{v_1 \cdot v_2}{c^2}} \] where \( v_{rel} \) is the relative speed, \( v_1 \) is your speed, \( v_2 \) is the truck's speed, and \( c \) is the speed of light.
02

Use the Formula for Part (a)

For part (a), we have your speed \( v_1 = 25 \) m/s and the truck's speed \( v_2 = 35 \) m/s. Substituting these into the formula: \[ v_{rel} = \frac{25 + 35}{1 + \frac{25 \cdot 35}{65^2}} \].
03

Compute the Value for Part (a)

Calculate the numerator: \( 25 + 35 = 60 \) m/s.
Calculate the denominator: \( 1 + \frac{25 \cdot 35}{65^2} \approx 1 + \frac{875}{4225} \approx 1.207 \)
Thus, \[ v_{rel} \approx \frac{60}{1.207} \approx 49.71 \text{ m/s} \].
04

Use the Formula for Part (b)

For part (b), substitute your speed \( v_1 = 5 \) m/s and the truck's speed \( v_2 = 55 \) m/s into the formula: \[ v_{rel} = \frac{5 + 55}{1 + \frac{5 \cdot 55}{65^2}} \].
05

Compute the Value for Part (b)

Calculate the numerator: \( 5 + 55 = 60 \) m/s.
Calculate the denominator: \( 1 + \frac{5 \cdot 55}{65^2} \approx 1 + \frac{275}{4225} \approx 1.065 \)
Thus, \[ v_{rel} \approx \frac{60}{1.065} \approx 56.34 \text{ m/s} \].

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Key Concepts

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

Speed of Light
In the realm of physics, the speed of light is a fundamental constant, denoted by \( c \). It represents the maximum speed at which information or matter can travel through a vacuum. While usually noted as approximately 299,792,458 meters per second in scientific contexts, in our exercise, it's been conveniently rounded to 65 m/s for simplification purposes. This speed is crucial when we deal with relativistic effects, which become significant when objects move at velocities approaching \( c \). The speed of light acts as a cosmic speed limit, setting boundary conditions for physical laws.
Understanding the implications of the speed of light in calculations helps us grasp why objects can't exceed this velocity. When velocities approach \( c \), time dilation and length contraction occur, reflecting how space and time intermingle at high speeds. This understanding is foundational in relativistic velocity addition, where classic assumptions of simple addition of velocities no longer hold.
Relative Speed
The concept of relative speed is about understanding the speed of one object as perceived from another object. In our real-world experiences, we typically add velocities directly. However, once we approach the speed of light, things change.

Using the relativistic velocity addition formula:
  • For any two objects with velocities, \( v_1 \) and \( v_2 \), relative speed \( v_{rel} \) is determined by the equation \( v_{rel} = \frac{v_1 + v_2}{1 + \frac{v_1 \cdot v_2}{c^2}} \), where \( c \) is the speed of light.
  • This equation shows us that relative speeds cannot simply be added without accounting for the relativistic factors.
Relativity tells us that as objects move faster and closer to the speed of light, their effective relative speeds are altered by the denominator, ensuring no relative speed exceeds \( c \). This relativistic effect is a direct consequence of the constancy of the speed of light in all reference frames.
Relativistic Physics
Relativistic physics refers to the study of physical phenomena at velocities close to the speed of light. In this domain, classical mechanics' predictions diverge significantly from observed reality. Relativistic effects become pronounced, requiring the use of Einstein's theory of relativity.

In everyday life, we mostly experience non-relativistic speeds, where classical mechanics suffice:
  • Time and space remain largely constant.
  • Velocities add linearly.
In contrast, when dealing with high speeds,
  • Time dilation occurs, meaning time can run slower for moving objects compared to those at rest.
  • Length contraction implies that an object's length can appear shorter as it approaches the speed of light.
  • Mass-like effects increase, meaning that more energy is required to continue accelerating an object already traveling close to \( c \).
These phenomena illustrate the fascinating and counterintuitive nature of high-speed physics, accurately described by relativistic equations, which ensure that speed, light, and reference frames interplay seamlessly to uphold consistent laws across the universe.

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Most popular questions from this chapter

Three particles are listed in the table. The mass and speed of each particle are given as multiples of the variables \(m\) and \(v,\) which have the values \(m=1.20 \times 10^{-8} \mathrm{kg}\) and \(v=0.200 \mathrm{c} .\) The speed of light in a vacuum is \(c=3.00 \times 10^{8} \mathrm{m} / \mathrm{s} .\) Determine the momentum for each particle according to special relativity. $$ \begin{array}{ccc} \text { Particle } & \text { Mass } & \text { Speed } \\ \hline \mathbf{a} & m & v \\ \hline \mathbf{b} & \frac{1}{2} m & 2 v \\ \hline \mathbf{c} & \frac{1}{4} m & 4 v \\ \hline \end{array} $$

ssm A particle known as a pion lives for a short time before breaking apart into other particles. Suppose that a pion is moving at a speed of \(0.990 c\), and an observer who is stationary in a laboratory measures the pion's lifetime to be \(3.5 \times 10^{-8}\) s. (a) What is the lifetime according to a hypothetical person who is riding along with the pion? (b) According to this hypothetical person, how far does the laboratory move before the pion breaks apart?

A woman is \(1.6 \mathrm{m}\) tall and has a mass of \(55 \mathrm{kg} .\) She moves past an observer with the direction of the motion parallel to her height. The observer measures her relativistic momentum to have a magnitude of \(2.0 \times 10^{10} \mathrm{kg} \cdot \mathrm{m} / \mathrm{s} .\) What does the observer measure for her height?

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A radar antenna is rotating and makes one revolution every 25 s, as measured on earth. However, instruments on a spaceship moving with respect to the earth at a speed \(v\) measure that the antenna makes one revolution every 42 s. What is the ratio o\(/ \mathrm{c}\) of the speed \(v\) to the speed \(c\) of light in a vacuum?

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