Question

You weight 300 N on Earth. A planet has three times the mass of Earth and four times the radius of the Earth. What is your weight in newtons on this planet

Answer 1

Are you familiar with Newton's universal law of gravitation?
\[F= \frac{GmM}{r^2}\]
All you have to do is to do a comparison.
Do you need further help?

Answer 2

Sweet. I posted this awhile ago. Thanks Shadow

Answer 3

You're welcome :) Your question is similar to his.

Answer 4

Yes i'm familiar with it

Answer 5

I did a ratio rather the gravitational force equation and solved for weight... but since I don't have mass for earth?

Answer 6

Shadow, if possible, can you help me on my own question? I do not want to further de-rail Swin's question.

Answer 7

\[ F_{earth} = \frac{Gm_{object} M_{earth}}{r^2_{earth}}\]---(1)
\[ F_{planet} = \frac{Gm_{object} M_{planet}}{r^2_{planet}}\]---(2)
Do a ratio of \(\frac{(1)}{(2)}\) and you should be able to get the answer.

Answer 8

So I find two ratios?

Answer 9

Yup. it's one actually. so \(\frac{F_{earth}}{F_{planet}}\)=?

Answer 10

So I'm confused. They give you the weight on earth. 3X is the planet's mass (of the earth) and the radius is 4X the earth. But that equation solves for the gravitational force? ugh idk, maybe I'm overthinking

Answer 11

Yup. weight on earth=\( F_{earth}\) where \(M_{planet}=3M_{earth} \)and so on

Answer 12

The gravitational pull of earth is your weight. so g is a variable.

Answer 13

Yeah, but what do I do with the 300 N?

Answer 14

or is the mass for Earth can be constant?

Answer 15

*any constant

Answer 16

300N = \(F_{earth}\)
M of earth , well, is a constant.

Answer 17

300 N/ Fplanet (3*1/(4^2)??

Answer 18

@Shadowys ? I feel like I'm doing this wrong lol

Answer 19

did you mean \(\frac{300N}{F_{planet}}= \frac{4^2}{3}\)?

Answer 20

Lol yess!!! I just put 300 N over a fraction/fraction :/ but yayyy right direction Thanks!!