A detector emits one pulse at a time. Each echo must return before the next pulse is emitted. The greatest distance to the reflecting surface is 75 m and the wave speed is 1500 m/s. Ignoring pulse duration, what is the maximum number of pulses emitted per second?
40 s−140\ \mathrm{s^{-1}}40 s−1
5 s−15\ \mathrm{s^{-1}}5 s−1
10 s−110\ \mathrm{s^{-1}}10 s−1
20 s−120\ \mathrm{s^{-1}}20 s−1
112 exam-style questions on Edexcel GCSE Physics 4.1 Wave properties, covering 4.1.1 Waves transfer energy and information, 4.1.2 Frequency, wavelength, amplitude, period and wavefronts, 4.1.3 Longitudinal and transverse waves, 4.1.4 The wave speed equations, 4.1.5 Measuring wave velocity, and 4.1.6 Calculating depth or distance from waves. Each one has a worked solution and a mark scheme showing where the marks go.