Question

1. Distinguish between inertial and accelerated frames of reference.

2.Consider two days when the air temperature is the same but the humidity is different. Which is more dense, the dry air or the humid air at the same T?

Answer 1

1)

Inertial frames are ones which are at rest or moving with uniform velocity with respect to fixed stars.
For an observer in such a frame of reference Newton's second law of motion is valid.

Ex: A train moving with uniform velocity is an inertial frame.

A non inertial frame is one which is accelerated ( linearly or due to rotation) with respect to fixed stars.
Newton's second law of motion is not valid in such a frame of reference, unless we introduce a force called pseudo - force.

Ex: A freely falling elevator may be taken as a non inertial frame.

2)

he units of density are mass divided by volume (m/V). Density will increase if either mass increases while the volume remains constant or if volume decreases while mass remains constant.

Density of air will vary as the temperature and moisture content in the air varies. When the temperature increases, the higher molecular motion results in an expansion of volume and thus a decrease in density.

The amount of water vapor in the air also effects the density. Water vapor is a relatively light gas when compared to diatomic Oxygen and diatomic Nitrogen. Thus, when water vapor increases, the amount of Oxygen and Nitrogen decrease per unit volume and thus density decreases because mass is decreasing.

The two most abundant elements in the troposphere are Oxygen and Nitrogen. Oxygen has an 16 atomic unit mass while Nitrogen has a 14 atomic units mass. Since both these elements are diatomic in the troposphere (O2 and N2), the atomic mass of diatomic Oxygen is 32 and the diatomic mass of Nitrogen is 28.