okay for a) I got the answer as 11.67 seconds and did v=d/t and for b) i found that wavelength= 6km. Im confused how the 100 m deep affects the equation for c and d.
The 2011 Japan tsunami was triggered by an earthquake 70 km offshore. The earthquake travels through the earth as a sound wave; the speed of sound in rock is 6 km/s. (a) How long after he earthquake happened was the earthquake felt in Japan? (b) The frequency of this sound wave is about 1 Hz, what was the wavelength? (c) The wavelength of the tsunami is hundreds of miles; the ocean is about 100m deep in that region. What was the tsunami wave speed? (d) How long did it take the tsunami to reach Japan?
To answer part (a), you correctly used the equation v = d/t, where v is the speed of sound in rock, d is the distance from the earthquake to Japan, and t is the time taken for the earthquake to be felt in Japan. Rearranging the equation, we have t = d/v. You correctly substituted the given values (v = 6 km/s and d = 70 km) to find t = 11.67 seconds.
For part (b), you correctly found the wavelength using the equation wavelength = speed of sound/frequency. The given frequency is 1 Hz, and the speed of sound in rock is 6 km/s. Substituting these values, you found the wavelength to be 6 km.
Moving on to part (c), the depth of the ocean affects the equation because it influences the speed of the tsunami. The speed of a tsunami wave is given by the equation speed = sqrt(gr), where g is the acceleration due to gravity and r is the water depth. As the water depth is 100 m (0.1 km), that value is substituted into the equation.
Finally, to answer part (d), you need to find the time taken for the tsunami to reach Japan. The formula to calculate time is t = d/speed, where d is the distance from the earthquake to Japan and speed is the tsunami wave speed that you calculated in part (c).