Calculate the gravitational force exerted on a 5.00 kg baby

[Mariesa Yeoman]

Homework Statement

Astrology, that unlikely and vague pseudoscience, makes much of the position of the planets at the moment of birth. The only known force a planet exerts on Earth is gravitational.
(a) Calculate the gravitational force exerted on a 5.00 kg baby by a 130 kg father 0.200 m away at birth (assisting so he is close).

(b) Calculate the force on the baby due to Jupiter if it is at its closest to the earth, some 6.29 ✕ 1011 m away, showing it to be comparable to that of the father. The mass of Jupiter is about 1.90 ✕ 1027 kg. Other objects in the room and the hospital building also exert similar gravitational forces. (Of course, there could be an unknown force acting, but scientists first need to be convinced that there is even an effect, much less that an unknown force causes it.)

Homework Equations

g = GM/ r² .

The Attempt at a Solution

I found a to be 0.00000108 N. I am struggling to find b) I have tried several times but seem to either be substituting the values wrong, or not understanding all together. Can someone explain how to do this problem?

 

[RPinPA]

g = GM/ r2

That is gravitational acceleration.

The gravitational force between mass $M$ and mass $m$, depends on both masses. It is $F = GMm/r^2$.
The acceleration that causes on mass $m$ is found from setting $F = ma$ or $a = F/m$ which gives $a = GM/r^2$.

Also a general comment that "I have tried but my answer is wrong" gives us no information on what you're doing, therefore no way to tell you what you might be doing wrong.

 

[Mariesa Yeoman]

I was able to solve it, thank you. I was leaving out the exponent on the radius, causing the calculation to be wrong.