Three independent measurements are made in an inspection laboratory.

PHYSICS · Multi-part · Fermi University Physics · Oscillations, Waves & Acoustics · Fluids & Continuum Physics · Superposition, boundaries and interference

Bending, Ringing, Breaking and Flowing, Ch Elastic waves in a solid and at its surface

Problem

Three independent measurements are made in an inspection laboratory. ((a)) A copper plate (density

8960\,\mathrm{kg\,m^{-3}}

, longitudinal wave speed

4.70\,\mathrm{km\,s^{-1}}

) is immersed in engine oil (density

850\,\mathrm{kg\,m^{-3}}

, wave speed

1.40\,\mathrm{km\,s^{-1}}

). A longitudinal pulse in the copper strikes the copper-oil interface at normal incidence. Find the fraction of the incident wave energy reflected back into the copper. ((b)) A seismometer records an S-P delay of

35.0\,\mathrm{s}

for an earthquake in crust that behaves as a Poisson solid (

\nu = 0.25

) with longitudinal speed

c_L = 6.5\,\mathrm{km\,s^{-1}}

. Find the distance from the station to the earthquake, assuming a uniform straight-line path. ((c)) A pulse-echo test on a titanium alloy block of thickness

15.0\,\mathrm{mm}

(density

4430\,\mathrm{kg\,m^{-3}}

) shows successive back-wall echoes every

4.92\,\mathrm{\mu s}

on the longitudinal transducer and every

9.62\,\mathrm{\mu s}

on the shear transducer. Find Young's modulus and Poisson's ratio of the block.

Browse the problem library