Calculating Acceleration Due to Gravity on the Moon and Mars

[cougar_21]

Ok, please tell me if i am correct, or totally out of it

What is the acceleration due to gravity on the surface of
(a) the Moon (R=1.74x10^3km, m= 7.35x10^22kg)
(b) Mars (R=3.40x10^3km, m= 6.42x10^23kg)

i used v= square root of m/R

for a i got 6.4993x 10^9
for b i got 1.3741 X 10^10

is this correct, cause i really am not confident

 

[cougar_21]

k i took a different approach please tell me which one is the correct one:
this time i took Gm/R^2 to get the acc.

for a i got 1.62 m/s^2
o.0 sorry i really have no clue what I am doing

 

[CartoonKid]

You should use the second one. Basically, they are all originated from $$\frac{GMm}{R^2}$$. You got the first one by equalling it to centripedal force and the second to $$mg$$.

 

[cougar_21]

k so then the second equation is the correct one? TY

Another question since the R is in km should I change it to meters?

 

[CartoonKid]

Yes, you have to change them to SI unit.

 

[Janus]

Another question since the R is in km should I change it to meters?

yes, you should.

 

[cougar_21]

thank you !