# Homework Help: Gravitation Force Between Two Massive Bodies

1. Oct 15, 2008

### tater08

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

The Stardust spacecraft was designed to visit a comet and bring samples of its material back to the earth. The craft is 1.7 m across and has a mass of 385 kg. In January 2004, from a distance of 237 km, it took the photograph of the nucleus of comet Wild2, shown in the figure below. The distance across this nucleus is 5 km, and we can model it as an approximate sphere. Since astronomers think that comets have a composition similar to that of Pluto, we can assume a density the same as Pluto's, which is 2.1 g/cm^3. The samples taken will be returned to earth on Jan. 15, 2006.

What gravitational force did the comet exert on the spacecraft

2. Relevant equations

F=G ((m1 * m2)/R^2) G= 6.674 x 10 ^-11

3. The attempt at a solution

Well the radius i determined to be 240.35 km. The mass of the satellite is 385 kg. I guess i'm having the problem of determing the mass of the comet. Please Help!!!

2. Oct 16, 2008

### tiny-tim

Hi tater08!

mass = volume times density.

3. Oct 16, 2008

### tater08

the volume of a sphere is 4/3 pi (2.5)^3 if the nucleus radius is 5km across the radius is 2.5 km. after converting the 2.1 g/cm^3 to 0.21 kg/m^3. 0.21 kg/m^3 = M/65449.85 m^3 M=13744.47kg F= G (m1 *m2)/R^2 F= (6.674 * 10 ^-11) ((13742.4kg)(385kg))/237000m F=6.29* 10^-15

is this right? Thanks for the help!

4. Oct 16, 2008

Nooo …