How long would it take a spacecraft traveling 0.980c to reach that star from Earth, as measured by observers on Earth

Wo audio speakers are placed on a vertical rail. speaker a is placed at head-level while speaker b is place at some variable height, \delta yδy, above speaker a. both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.531 meters. calculate the lowest height that speaker b can be placed above speaker a to produce a minimum of sound heard by person standing \delta x = 7.86δx=7.86 meters directly in front of speaker a.

What are similarities and differences between refraction, reflection, diffraction and absorption?

The government has declared that a hurricane is likely to hit the east coast. which government division is part of acf and provides guidance to citizens? a. job opportunities for low-income individuals b. office of human services emergency preparedness and response c. assets for independence d. low-income home energy assistance program