A person, with his ear to the ground, sees a huge 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 0.90 s apart. The speed of sound in air is 343 m/s, and in concrete is 3000 m/s. How far away did the impact occur? Speed of Sound in Various Materials(20°C and 1 atm)
Material Speed (m s)
Air 343
Air (0°C) 331
Helium 1005
Hydrogen 1300
Water 1440
Sea water 1560
Iron and steel ≈ 3000
Glass ≈ 4000
Aluminum ≈ 5100
Hardwood ≈ 4500
Concrete ≈ 5000