The free-fall acceleration on the surface of planet A is about one tenth of that on the surface of planet B. If the radius of planet A is a quarter of the radius of planet B (RB/4), find the ratio of their average densities?

Respuesta :

Answer:

[tex]\frac{\rho_A}{\rho_B} = 0.4[/tex]

Explanation:

As we know that the acceleration due to gravity on the surface of the planet is given as

[tex]a = \frac{GM}{R^2}[/tex]

so we will have

M = mass of the planet

[tex]M = \rho (\frac{4}{3} \pi R^3)[/tex]

so we have

[tex]a = \frac{G \rho \frac{4}{3} \pi R^3}{R^2}[/tex]

[tex]a = \frac{4}{3}\rho \pi G R[/tex]

so we have

[tex]\frac{a_A}{a_B} = \frac{\rho_A R_A}{\rho_B R_B}[/tex]

[tex]\frac{1}{10} = \frac{\rho_A (R_B/4)}{\rho_B R_B}[/tex]

[tex]\frac{1}{10} = \frac{\rho_A}{4\rho_B}[/tex]

[tex]\frac{\rho_A}{\rho_B} = 0.4[/tex]