Question 1
A person sees a heavy stone strike the concrete pavement. A moment later two sounds are heard from the impact: one travels in the air and the other in the concrete, and they are 1.07s apart. How far away did the impact occur? Take the speed of sound in concrete as 2.95x103 m/s and give your answer in km.
Question 2
A 50dB sound wave strikes an eardrum whose area is 5.6x10-5 m2. How much energy is absorbed by the eardrum per second?
Take the threshold of hearing to be Io = 10-12 W/ m2 and give your answer in pico-Joules, where 1pJ =10-12 J