So-called volcanic "ash" is actually finely pulverized rock blown high into the atmosphere. A typical ash particle is a 50-μm-diameter piece of silica with a density of 2400 kg/m3. How long in hours does it take this ash particle to fall from a height of 5.0 km in still air? Use the properties of 20∘C air at sea level.

So-called volcanic "ash" is actually finely pulverized rock blown high into the atmosphere. A typical ash particle is a 50-μm-diameter piece of silica with a density of 2400 kg/m3. How long in hours does it take this ash particle to fall from a height of 5.0 km in still air? Use the properties of 20∘C air at sea level.