Gravitational force between 2 particles

[clope023]

Homework Statement

A uniform, solid, 1900kg sphere has a radius of 5.00m. Find the gravitational force this sphere exerts on a 1.50kg point mass placed at the following distances from the center of the sphere: (a) 5.01m , and (b) 2.45m.

Homework Equations

Fg = GMm/r^2

volume of sphere = (4/3)piR^3

density of sphere = M/volume

ratio of point mass to shere:

M/msphere = (4/3piRM^3)/(4/3piRsphere^3)

Mmass = msphere(Rmass/Rsphere)^3

G(M)(mmass)/r^2 = Gmass(msphere(rmass/rsphere)^3)/Rsphere^2

= G(mmass)(msphere)rmass/rsphere

The Attempt at a Solution

Fg = G(1900)(1.50)(5.01)/5^2 = 3.8x10^-7

Fg = G(1900)(1.50)/5^2 = 8x10^-8

nothing, I'm not sure what I'm doing wrong, any help is greatly appreciated.

 

[Snazzy]

Homework Statement

A uniform, solid, 1900kg sphere has a radius of 5.00m. Find the gravitational force this sphere exerts on a 1.50kg point mass placed at the following distances from the center of the sphere: (a) 5.01m , and (b) 2.45m.

Homework Equations

Fg = GMm/r^2

volume of sphere = (4/3)piR^3

density of sphere = M/volume

ratio of point mass to shere:

M/msphere = (4/3piRM^3)/(4/3piRsphere^3)

Mmass = msphere(Rmass/Rsphere)^3

G(M)(mmass)/r^2 = Gmass(msphere(rmass/rsphere)^3)/Rsphere^2

= G(mmass)(msphere)rmass/rsphere

The Attempt at a Solution

Fg = G(1900)(1.50)(5.01)/5^2 = 3.8x10^-7

Fg = G(1900)(1.50)/5^2 = 8x10^-8

nothing, I'm not sure what I'm doing wrong, any help is greatly appreciated.

Where are the 5^2 coming from?

 

[Moetasim]

Your calculations seem to be correct. However, it is important to remember that the gravitational force is a vector quantity, meaning it has both magnitude and direction. In this case, the direction of the force would be towards the center of the sphere. So, your final answers should include a direction component as well. Additionally, it is good practice to include units in your calculations and final answers. In this case, the units for gravitational force would be Newtons (N). So, your final answers would be 3.8x10^-7 N and 8x10^-8 N, respectively. Keep up the good work!