Question

Dewayne reviews Kepler’s laws by making the table shown. Which label belongs in each cell of the table?

W: The orbital period is related to the average distance from the Sun.
X: Orbit are ellipses with the Sun at a focus.
Y: A planet sweeps out equal areas in equal time frames as it orbits the Sun.

Choices:
A. W: First
X: Second
Y: Third

B. W: Third
X: Second
Y: First

C. W: Third
X: First
Y: Second

D. W: Second
X: Third
Y: First

Answer 1

There are three laws which are postulated by Kepler for planetary motion.

Kepler's first law: As per the first law of Kepler,the orbits of planets around the sun is elliptical in nature in stead of circular. The sun is situated always at one of its foci.

Second law: Planets are moving in such a way that the areal velocity of the planets are constant i.e planets sweep out equal ares in equal interval of time.

Third law: The square of time period of planets around the sun is directly proportional to the cube of semi major axis.

       $Mathematically\ T^{2} \alpha\ R^{3}$

where T is the time period and R is semi major axis.

Hence the correct answer to the question is C i.e third,first,second.

Answer 2

Explanation :

Kepler gives three laws of planetary motion :

First law :

First law is also known as the law of orbits. It states that all planets revolve in an elliptical orbit. The sun is present at one of its foci.

Second law :

Second law is also known as the law of areas. It states that draw a hypothetical line from the midpoint of the sun to the midpoint of the planet. This will sweep out the same areas in identical interval of time.

Third law :

This is also known as the law of periods. It states that the square of the orbital time period (T) is directly proportional to the cube of semi-major axis (a).

i.e. $T^2\propto a^3$

So, Correct labeling is :

W: Third law

X: First law

Y: Second law

Hence, the correct option is (C).