A 2.0m long aluminium rod is held horizontally in air. One end of the rod is struck sharply with a hammer. At the other end, two microphones are fixed side by side: microphone A is attached directly to the rod, while microphone B is suspended in air 2.0m away from the point of impact. Both microphones are connected to the same oscilloscope, which shows that the signal from microphone A reaches 5.1ms earlier than the signal from microphone B. (Take the speed of sound in air as 340m/s.)
(a) Give a reason why two distinct signals are observed on the oscilloscope for a single hammer strike.
(b) Using the data provided, calculate the speed of longitudinal sound waves in aluminium.
(c) State, with justification, whether aluminium is a better or poorer conductor of sound than air.