Calculate gravitational field strength above surface of Mars

[TalliThePrune]

1. Calculate the gravitational field strength at 500km above Mars' surface.
Mass of Mars: 6.39 x 10²³ kg
Radius of Mars: 3.39 x 10³ km
Constant G: 6.67 x 10^-11

2. I used the equation g = GM / r²3. To begin with I added the 500km height above ground to the radius, giving 3.89 x 10³ km. I then converted this to metres, which is 3.89 x 10⁶ m.

So subbing this into the formula:
(6.67 x 10^-11) x (6.39 x 10²³) / (3.89 x 10⁶)²

= 2.82 N/kg

Is this correct? Thanks in advance!

 

[gneill]

Looks fine!

 

[TalliThePrune]

Thank you!

 

[andrevdh]

I get 3.71 m/s² ?

 

[TalliThePrune]

@andrevdh , did you use the same formula / figures as I did in the OP?

I'm very worried about doing this wrong as I have an exam tomorrow.

 

[SteamKing]

I get 3.71 m/s² ?

This figure is OK, if you are at the surface of Mars. However, the OP asks for the value of gravitational acceleration 500 km above the surface of Mars.

 

[TalliThePrune]

This figure is OK, if you are at the surface of Mars. However, the OP asks for the value of gravitational acceleration 500 km above the surface of Mars.

Ah! Thanks so much for clarifying, I was too stressed to spot what he'd done.