A slinky wave is analysed using two separate graphs drawn on square-grid papers.
1. Displacement–distance graph: each horizontal square represents 0.40cm. The horizontal span between the first crest and the third crest covers 15 such squares.
2. Displacement–time graph: each horizontal square represents 1ms. The horizontal span between the first trough and the third trough covers 8 such squares.
Determine the speed of the wave.
(a) 15m/s
(b) 3.75m/s
(c) 7.5m/s
(d) 11.25m/s