Q.A force of 339 N is applied horizontally to a wooden crate in order to displace it 35.0 m across a level floor at a constant velocity. As a result of this work the crate's internal energy is increased by an amount equal to 15 percent of the crate's initial internal energy. Calculate the initial internal energy of the crate.
Q. Calculate the mean scattering cross-section at a frequency of 5 MHz of a distribution of air bubbles of 3 μm mean radius, assuming a Gaussian size distribution of a variance of 1 μm and 1.5 μm. The total damping constant is 1.0. The total number of air bubbles is 100,000. Repeat these calculations at 4 MHz and 6 MHz for variance = 1 μm. Discuss the effects of size distribution and bandwidth on the mean scattering cross-section.