A 15-cm c m -tall closed container holds a sample of polluted air containing many spherical particles with a diameter of 2.5 μm μ m and a mass of 1.1 × × 10−14 − 14 kg k g . How long does it take for all of the particles to settle to the bottom of the container?

Ahuge (essentially infinite) horizontal nonconducting sheet 10.0 cm thick has charge uniformly spread over both faces. the upper face carries +95.0 nc/m2 while the lower face carries -25.0 nc/ m2. what is the magnitude of the electric field at a point within the sheet 2.00 cm below the upper face? (ε0 = 8.85 × 10-12 c2/n · m2)