HW Question, very simple. mass/gravity

[ek378996]

If a planet is 1/2 of earth, gravitational is the same of earth, what does that tell you about the mass?

 

[rock.freak667]

If a planet is 1/2 of earth

half the size?

anyhow...What is mass affected by?

 

[ek378996]

yes, half the size. Nothing, just trying to find out if the mass of the planets is 2 or 4 times larger/smaller than earth.

basically if a planet is half the size of the earth, and gravitation is the same as earth, what would the planets mass have to be? 2 or 4 times larger than earth?

 

[nikkor180]

Greetings:

If acceleration due to gravity is equal for both the Earth and another planet, then,

Gm_e / r_e² = Gm_p / r_p².
==> m_e = (r_e / r_p)² m_p
==> m_e = (2r_p / r_p)² (given r_e = 2r_p)
==> m_e = 4m_p

Regards,

Rich B.
rmath4u2@aol.com