Gravitational force

[Aikenfan]

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

http://i103.photobucket.com/albums/m121/aiken91919/1.jpg

I just need help with part 3, if anyone can help me, i don't really know what to do

2. Relevant equations
F=k(q1)(q2)/r^2

3. The attempt at a solution

[giritrobbins]

It is simple Newtonian Gravitation.
F=G(mp)^2/r^2

mp=mass of a proton
G=Universal graviational constant
mp is squared because it is two protons, otherwise it would be m1 and m2

[Aikenfan]

G is constant, but i am unsure of how to get mp

[giritrobbins]

The mass of a proton is constant. It should be locatable in any physics book or going to google and typing mass of a proton

[Aikenfan]

Okay, i got: 16726E-27^2 * G / .0071^2
= 3.6627E-52

[Aikenfan]

i submitted it but got it wrong, but i have a few more tries to get it right, what did i do wrong?

[hage567]

That’s 1.6726x10^-27 kg for the mass of a proton, right? It looks like you were missing the decimal in there.

[Aikenfan]

now i got 3.66e-60

[hage567]

Did it work? It should.

[Aikenfan]

it says it is wrong, not sure why though, i double checked. it seems like it should be right

[hage567]

Well, I get 3.70x10^-60 N, so maybe it is a rounding issue? I don't know how picky web programs are about that kind of thing. I can't see why the answer would be wrong.

[Aikenfan]

i have 1 guess left, i will try 3.70x10^-60 N

[Aikenfan]

hmm maybe not, one of my previous guesses was 3.69e-60, that probably should have been correct

[hage567]

Sorry, I just am not able to see what could be wrong with that calculation.

[Aikenfan]

thank you for all of your help

[Aikenfan]

i got it incorrect, but the answer was 3.811e-60
have no idea how they got that, ill have to check with my teacher because i still think the other answer is correct, maybe it is a mistake

[hage567]

A different value for the proton mass was probably used. If I work it out backwards I get 1.697x10^-27 kg for the mass. Not the right one as far as I'm concerned.

[Aikenfan]

i think i will ask my teacher, maybe she will give it to me
thank you very much for all of the help!

[neutrino]

It may be, just may be, that the program assumes the value of the proton mass to be 1.67e-27 - just to two decimal places.