Select the correct answer.

Kepler's third law can be used to derive the relation between the orbital period, [tex]P[/tex] (measured in days), and the semimajor axis, [tex]A[/tex] (measured in AU), of an orbiting body. The relation is given by the equation [tex]P^2 = k A^3[/tex], where [tex]k[/tex] is a constant value for all bodies orbiting that star. The semimajor axis of Mars is 1.52 AU, and its orbital period is about 687 days. What is the value of the constant [tex]k[/tex]?

A. [tex]4.52 \times 10^2[/tex]
B. [tex]7.44 \times 10^{-6}[/tex]
C. [tex]1.34 \times 10^5[/tex]
D. [tex]2.21 \times 10^{-3}[/tex]



Answer :

Given Kepler's third law, which states that [tex]\( P^2 = k \cdot A^3 \)[/tex], we need to find the value of the constant [tex]\( k \)[/tex] for Mars. We have the following given values:

- Orbital period of Mars ([tex]\( P \)[/tex]): 687 days
- Semimajor axis of Mars ([tex]\( A \)[/tex]): 1.52 AU

According to Kepler's third law:

[tex]\[ P^2 = k \cdot A^3 \][/tex]

First, we will square the orbital period ([tex]\( P \)[/tex]):

[tex]\[ 687^2 \][/tex]

Then we will cube the semimajor axis ([tex]\( A \)[/tex]):

[tex]\[ 1.52^3 \][/tex]

To isolate [tex]\( k \)[/tex], we rearrange the equation to:

[tex]\[ k = \frac{P^2}{A^3} \][/tex]

Substituting the known values into the equation:

[tex]\[ k = \frac{687^2}{1.52^3} \][/tex]

Calculating [tex]\( 687^2 \)[/tex]:

[tex]\[ 687^2 = 471969 \][/tex]

Calculating [tex]\( 1.52^3 \)[/tex]:

[tex]\[ 1.52^3 = 3.511328 \][/tex]

Finally, we divide the squared orbital period by the cubed semimajor axis to find [tex]\( k \)[/tex]:

[tex]\[ k = \frac{471969}{3.511328} \approx 134394.87580186615 \][/tex]

From the given options, the closest value to this result is:

C. [tex]\( 1.34 \times 10^5 \)[/tex]

So, the correct answer is:

C. [tex]\( 1.34 \times 10^5 \)[/tex]