Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 16: Problem 11

A (somewhat risky) way of telling if a train that cannot be seen or heard is approaching is by placing your ear on the rail. Explain why this works.

Short Answer

Expert verified
Answer: Placing your ear on a railway track helps detect an approaching train because sound waves travel faster and more efficiently through the solid steel track than through air, allowing you to sense the vibrations created by the train's movement even if it's too far away to be heard through the air. However, this method is not recommended for safety reasons as it puts individuals at risk of being too close to the tracks when a train approaches.

Step by step solution

01

Understanding sound waves

Sound is a vibrational energy transmitted through mediums like air, water, and solids. The vibration causes the particles in the medium to oscillate back and forth, creating sound waves. These sound waves are longitudinal waves that travel at different speeds depending on the medium.
02

Properties of solids for sound transmission

In solids, particles are more densely packed than in air or water, allowing them to transmit sound waves faster and more efficiently. The speed of sound in steel, which is the primary material used in railway tracks, is around 5,120 meters per second (m/s), while in air, it is approximately 343 m/s. Thus, sound travels significantly faster through steel than through air.
03

Detecting vibrations through the ear

Our ears can detect the vibrations created by sound waves in the environment. When you place your ear on a solid surface, like a railway track, you can effectively detect the vibrations that travel along the track. This means that if a train is approaching, even from a distance, the vibrations from the train's movement will propagate through the steel track and your ear will sense the vibrations more easily when in direct contact with the track.
04

Why it works for detecting approaching trains

Placing your ear on the railway track allows you to effectively detect an approaching train because the solid track can transmit the sound waves faster and more efficiently than through air. As a result, you can sense the vibrations created by the train's movement even if it's too far away to be heard through the air. This helps in determining if a train is coming without actually seeing or hearing it through the air, although it is a risky method and not recommended for safety reasons.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

At a state championship high school football game, the intensity level of the shout of a single person in the stands at the center of the field is about \(50 \mathrm{~dB}\). What would be the intensity level at the center of the field if all 10,000 fans at the game shouted from roughly the same distance away from that center point?

A meteorite hits the surface of the ocean at a speed of \(8800 \mathrm{~m} / \mathrm{s}\). What are the shock wave angles it produces (a) in the air just before hitting the ocean surface, and (b) in the ocean just after entering? Assume the speed of sound in air and in water is \(343 \mathrm{~m} / \mathrm{s}\) and \(1560 \mathrm{~m} / \mathrm{s}\), respectively.

You are driving along a highway at \(30.0 \mathrm{~m} / \mathrm{s}\) when you hear a siren. You look in the rear-view mirror and see a police car approaching you from behind with a constant speed. The frequency of the siren that you hear is \(1300 \mathrm{~Hz}\). Right after the police car passes you, the frequency of the siren that you hear is \(1280 \mathrm{~Hz}\). a) How fast was the police car moving? b) You are so nervous after the police car passes you that you pull off the road and stop. Then you hear another siren, this time from an ambulance approaching from behind. The frequency of its siren that you hear is \(1400 \mathrm{~Hz}\). Once it passes, the frequency is \(1200 \mathrm{~Hz}\). What is the actual frequency of the ambulance's siren?

A soprano sings the note \(C 6(1046 \mathrm{~Hz})\) across the mouth of a soda bottle. To excite a fundamental frequency in the soda bottle equal to this note, describe how far the top of the liquid must be below the top of the bottle.

A classic demonstration of the physics of sound involves an alarm clock in a bell vacuum jar. The demonstration starts with air in the vacuum jar at normal atmospheric pressure and then the jar is evacuated to lower and lower pressures. Describe the expected outcome.
See all solutions

Recommended explanations on Physics Textbooks

Translational Dynamics

Read Explanation

Engineering Physics

Read Explanation

Astrophysics

Read Explanation

Magnetism and Electromagnetic Induction

Read Explanation

Electrostatics

Read Explanation

Quantum Physics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free