To determine the speed of a longitudinal wave pulse in a tensioned steel cable, a group of students stretch a 45 m cable between two fixed anchors. One student strikes one end with a hammer to initiate a wave pulse. A second student, standing at the far end, starts a manual stopwatch when they see the hammer strike and stops it when they feel the vibration arrive.
They record the following travel times across four successive trials:
Explain why the recorded times vary so significantly between trials.