Units Dimensions And Measurements

To compare energy units, we convert all to joules: \begin{itemize} \item \item \item \item \end{itemize} Among the given options, Joule is the largest unit.

Plane angle and solid angle are considered dimensionless physical quantities in the SI system.
However, they do possess units — the radian (rad) for plane angle and steradian (sr) for solid angle.
Since these quantities represent ratios (arc length to radius for plane angle and area to radius squared for solid angle), they have no physical dimensions, even though they are assigned standard units.

Step 1: Understand what AU stands for
AU is the abbreviation for Astronomical Unit, which is a unit of measurement used in astronomy.
Step 2: Definition of Astronomical Unit
1 AU is defined as the average distance between the Earth and the Sun. This distance is approximately 149.6 million kilometers (93 million miles).
Step 3: Common uses of AU
Astronomers use AU to measure: - Distances between objects within our solar system - Orbital distances of planets - Distances to nearby stars
Step 4: Why other options are incorrect
(A) Temperature - Measured in Kelvin, Celsius or Fahrenheit
(C) Weight - Measured in Newtons or pounds
(D) Time - Measured in seconds, hours, years etc.
Step 5: Importance of AU
The AU provides a convenient scale for measuring solar system distances without using extremely large numbers in kilometers or miles.

An Astronomical Unit (AU) is defined as the mean distance between the Earth and the Sun.
Its approximate value is meters.
It serves as a convenient unit for measuring distances within our solar system.