At a sudden contraction in a pipe the diameter changes from d1 to d2. the pressure drop, δp, which develops across the contraction is a function of d1 and d2, as well as the velocity, v, in the larger pipe, and the fluid density, and viscosity, use d1, v, and as repeating variables to determine a suitable set of dimensionless parameters. why would it be incorrect to include the velocity in the smaller pipe as an additional variable?

Some material consisting of a collection of microscopic objects is kept at a high temperature. a photon detector capable of detecting photon energies from infrared through ultraviolet observes photons emitted with energies of 0.3 ev, 0.5 ev, 0.8 ev, 2.0ev, 2.5ev, and 2.8ev. these are the only photon energies observed. (a) draw and label a possible energy-level diagram for one of the microscopic objects, which has four bound states. on the diagram, indicate the transitions corresponding to the emitted photons. explain briefly. (b) would a spring–mass model be a good model for these microscopic objects? why or why not? (c) the material is now cooled down to a very low temperature, and the photon detector stops detecting photon emissions. next, a beam of light with a continuous range of energies from infrared through ultraviolet shines on the material, and the photon detector observes the beam of light after it passes through the material. what photon energies in this beam of light are observed to be significantly reduced in intensity (“dark absorption lines”)? explain briefly.

Ideal meters problem. what internal resistance is ideal for a voltmeter? what internal resistance is ideal for an ammeter?

Bonds within one water molecule are examples of