Question

2.20 The nearest star to our solar system is 4.29 light years away. How much is this
distance in terms of parsecs? How much parallax would this star (named Alpha
Centauri) show when viewed from two locations of the Earth six months apart in its
orbit around the Sun ?
2.21 Precise measurements of physical quantities are a need of science. For example, to
ascertain the speed of an aircraft, one must have an accurate method to find its
positions at closely separated instants of time. This was the actual motivation behind
the discovery of radar in World War II. Think of different examples in modern science
where precise measurements of length, time, mass etc. are needed. Also, wherever
you can, give a quantitative idea of the precision needed.
2.22 Just as precise measurements are necessary in science, it is equally important to be
able to make rough estimates of quantities using rudimentary ideas and common
observations. Think of ways by which you can estimate the following (where an
estimate is difficult to obtain, try to get an upper bound on the quantity) :
(a) the total mass of rain-bearing clouds over India during the Monsoon
(b) the mass of an elephant
(c) the wind speed during a storm
(d) the number of strands of hair on your head
(e) the number of air molecules in your classroom.
2.23 The Sun is a hot plasma (ionized matter) with its inner core at a temperature exceeding
107 K, and its outer surface at a temperature of about 6000 K. At these high
temperatures, no substance remains in a solid or liquid phase. In what range do you
expect the mass density of the Sun to be, in the range of densities of solids and
liquids or gases? Check if your guess is correct from the following data : mass of the
Sun = 2.0 x1030 kg, radius of the Sun = 7.0 x 108 m.
2.24 When the planet Jupiter is at a distance of 824.7 million kilometers from the Earth,
its angular diameter is measured to be 35.72" of arc. Calculate the diameter of
Jupiter​

Answer 1

$\huge\mathtt\red{AnSwer}$

The nearest star to our solar system is 4.29 light years away. How much is this

distance in terms of parsecs? How much parallax would this star (named Alpha

Centauri) show when viewed from two locations of the Earth six months apart in its

orbit around the Sun ?

2.21 Precise measurements of physical quantities are a need of science. For example, to

ascertain the speed of an aircraft, one must have an accurate method to find its

positions at closely separated instants of time. This was the actual motivation behind

the discovery of radar in World War II. Think of different examples in modern science

where precise measurements of length, time, mass etc. are needed. Also, wherever

you can, give a quantitative idea of the precision needed.

Answer 2

Explanation:

Units and Measurement

The nearest star to our solar system is 4.29 light years away. How much is this distance in terms of parsecs? How much parallax would this star (named AlphaCentauri) show when viewed from two locations of the Earth six months apart in its orbit around the Sun ? S = 2πr (r + h).