The most dangerous particles in polluted air are those with diameters less than 2.5 mm because they can penetrate deeply into the lungs. a 15-cm-tall closed container holds a sample of polluted air containing many spherical particles with a diameter of 2.5 mm and a mass of 1.4 * 10-14 kg. how long does it take for all of the particles to settle to the bottom of the container?

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.

Sound travels slower in colder air that it does in warmer air. make a claim about the effect of air temperature on the speed of sound. support your claim with evidence