1. Feb 1, 2010

### Afide

1. The problem statement, all variables and given/known data

The problem is to find what 150lbs on earth = Xlbs on mars.

2. Relevant equations

F=G(m1)m2/d^2

G = 6.67x10^-11 (obviously)

3. The attempt at a solution

I'm getting incredibly annoyed because he gave us the wrong units etc, and we didn't even go over this in class. The last time I did this was in Highschool Physics...

150lbs = 68KG

mars has .108 the mass of Earth and the diameter is 6,787KM

FG (W) = 6.67x10^-11 (68 KG) 6.45x10^23 KG
___________________________ = 8.63 newtons?...
3393.5^2 KM

I know my answer needs to be 249N which = 56lbs (I went onto an online calculator thing)

Last edited: Feb 1, 2010
2. Feb 1, 2010

### AEM

Check your units. Shouldn't you have the units of Mars' radius in meters? Make sure your units for G go with your other units.

3. Feb 2, 2010

### Staff: Mentor

This might be easier to solve using ratios.

$$F_e = \frac{GmM_e}{R_e^2}$$

$$F_m = \frac{GmM_m}{R_m^2}$$

Divide to find Fm/Fe. Doing it this way, several things cancel and you don't have to worry about converting units.