Gravitational force - I translating the wording into the formula

[lesdayy]

Homework Statement

Two masses are attracted by a gravitational force of 8.6 N. What will the force of attraction be if the distance between the two masses is quadrupled? (Round the final answer to four decimal places.)


Answer: The force of attraction will be _______N.

Relevant Equations

F = G(m1m2) / R2

i spoke to my proffesor about it but all he said was to put 1 in m1 and m2... for r^2 since it says to quadruple to just put 4^2

I asked about the G in the equation but he said not to worry about iit and pretend its not there...

 

[hmmm27]

Just to make sure, you know the 'R' in the equation refers to the distance between centers of mass, right ? Presumably, that is also what the word 'distance' means in the problem statement.

 

[phyzguy]

You don't need to know G or m1 or m2. You should think about why that is the case.

 

[kuruman]

You don't even need to know the distances. Also, be careful how you interpret the "relevant equation" G(m1m2) / R2 that you posted. m1 stands for "mass 1" and m2 stands for "mass 2" but R2 does not stand for "distance 2".

 

[lesdayy]

Just to make sure, you know the 'R' in the equation refers to the distance between centers of mass, right ? Presumably, that is also what the word 'distance' means in the problem statement.

yes

 

[lesdayy]

You don't even need to know the distances. Also, be careful how you interpret the "relevant equation" G(m1m2) / R2 that you posted. m1 stands for "mass 1" and m2 stands for "mass 2" but R2 does not stand for "distance 2".

doesnt r stand for the distance or radious?

 

[kuruman]

doesnt r stand for the distance or radious?

Yes, it does. I was referring to number 2 next to R. It is R² unlike m₁ and m₂.

 

[berkeman]

Homework Statement:: Two masses are attracted by a gravitational force of 8.6 N. What will the force of attraction be if the distance between the two masses is quadrupled? (Round the final answer to four decimal places.)Answer: The force of attraction will be _______N.
Relevant Equations:: F = G(m1m2) / R2

It's best to use LaTeX to type math equations. It makes the equations much easier to read, and helps to avoid ambiguities like is "R2" really ##R^2## or ##R_2##

Your equation in LaTeX is:
$$F = G \frac{m_1 m_2}{R^2}$$
So if you quadruple the separation distance R, what does that do to the force F?

(See the "LaTeX Guide" link at the bottom of the Edit window to start learning how to post equations at PF)

 

[Steve4Physics]

Hi @lesdayy. Here are some questions for you to try. If you can work out how to do them, you should be able to answer your original question.

In the following questions ‘k’ is a constant (fixed value). If it helps, choose any values of k you want (e.g. k = 1 or 2 or 10) to help you answer the questions.
__________

Q1. Look at the equation y = kx. If x is tripled:
A) y is unchanged
B) y increases by a factor 3
C) y increases by a factor k
D) y increases by a factor 3k
E) none of the above and/or insufficient information
Choose one answer.

Q2. Look at the equation y = kx². If x is tripled:
A) y increases by a factor 3
B) y increases by a factor 9
C) y increases by a factor 3k²
D) y increases by a factor 9k
E) none of the above and/or insufficient information
Choose one answer.

Q3. Look at the equation ##y = \frac {k}{x²}##. If x is tripled:
A) y decreases by a factor 3
B) y decreases by a factor 9
C) y changes by a factor ##\frac {k²}{9}##
D) y changes by a factor ##\frac k 9##
E) none of the above and/or insufficient information
Choose one answer.