Engineering Applications

Millennium Bridge: Driven Lateral Vibration

When the Millennium Bridge in London opened in 2000, pedestrian motion and the bridge's lateral response became coupled: people tended to synchronize their steps with the moving deck, reinforcing lateral excitation. Explain why added damping reduces the response without treating the event as a simple undamped oscillator.

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P- and S-Wave Arrival-Time Interpretation

An earthquake generates P-waves and S-waves. Explain what a station learns from their different particle motions and arrival times, and distinguish source distance from epicenter location.

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Simple Harmonic Motion (SHM) Examples

Mass–Spring Period and Frequency

A 2.0 kg2.0 \text{ kg} mass is attached to a horizontal spring with a spring constant k=50 N/mk = 50 \text{ N/m}. The mass is displaced 0.1 m0.1 \text{ m} from equilibrium and released from rest. What is the period and frequency of the oscillation?

Mass-Spring Period Diagram

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Simple Pendulum on the Moon

An astronaut on the Moon wants to create a simple pendulum that has a period of exactly 2.0 seconds2.0 \text{ seconds}. If the acceleration due to gravity on the Moon is 1.62 m/s21.62 \text{ m/s}^2, how long must the pendulum string be?

Lunar Pendulum Diagram

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Energy Conservation in a Mass–Spring Oscillator

A 0.5 kg0.5 \text{ kg} block attached to a spring (k=200 N/mk = 200 \text{ N/m}) oscillates on a frictionless horizontal surface. If its maximum speed (velocity at equilibrium) is 3.0 m/s3.0 \text{ m/s}, what is the amplitude of the oscillation?

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Wave Properties and Speed Examples

Radio-Wave Wavelength from Frequency

A radio station broadcasts an FM radio wave (an electromagnetic wave traveling at the speed of light, c=3.0×108 m/sc = 3.0 \times 10^8 \text{ m/s}) at a frequency of 95.5 MHz95.5 \text{ MHz}. What is the wavelength of the radio wave?

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Wave Speed on a Tensioned String

A 2.0 m2.0 \text{ m} long guitar string has a mass of 0.005 kg0.005 \text{ kg}. It is pulled tight with a tension of 400 N400 \text{ N}. If the string is plucked, how fast does the transverse wave pulse travel along the string?

Tensioned-String Wave-Speed Diagram

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Open-Pipe Fundamental and Second Harmonic

An organ pipe that is open at both ends has a fundamental frequency (first harmonic) of 250 Hz250 \text{ Hz}. If the speed of sound in air is 340 m/s340 \text{ m/s}, how long is the pipe? What is the frequency of its second harmonic?

Open-Pipe Standing-Wave Diagram

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Temporal Beat Frequency from Two Nearby Tones

Two coherent sound waves at the same observation point have frequencies fA=256 Hzf_A=256\text{ Hz} and fB=260 Hzf_B=260\text{ Hz} with comparable amplitudes. Determine the beat frequency and the time between successive amplitude maxima.

Temporal Beat Envelope Diagram

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