[Wevie]

Two problems from chemistry class that I just can't figure out where to begin:

Two Uranium nucleii are placed 1.00 cm apart.  What are the attractive forces and what are the repulsive forces acting on them?

I assume that I need to use Newtons gravitaional law formula for the attractive force and Coulomb's law for the repulsive.

Newtons law:  F=-G(m1*m2/r^2)

where
G=gravitational constant (6.67e-11)
m1 and m2 mass in kg of objects (Uranium nucleii) (I'm getting 3.9526e-25 kg)
r=distance in meteres (.01 m)

so:  -6.67e-11 ( 3.9526e-25*3.9526e-25 / .01^2)

-1.04e-55

but...  this is a multiple choice question and that answer is not even close to any of the available answers.

For the second part I assume I need to use Coulombs law

F=kc(q1*q2/r^2)

Where
q1 and q2 are the charges on the particles (in what units? Coulomb's?  How do I find this?)
r is the distance between the objects (in meters)
kc is the electrostatic constant - 8.854e-12

Thanks in advance for any and all advice!

[Yggdrasil]

Two problems from chemistry class that I just can't figure out where to begin:

Two Uranium nucleii are placed 1.00 cm apart.  What are the attractive forces and what are the repulsive forces acting on them?

I assume that I need to use Newtons gravitaional law formula for the attractive force and Coulomb's law for the repulsive.

Newtons law:  F=-G(m1*m2/r^2)

where
G=gravitational constant (6.67e-11)
m1 and m2 mass in kg of objects (Uranium nucleii) (I'm getting 3.9526e-25 kg)
r=distance in meteres (.01 m)

so:  -6.67e-11 ( 3.9526e-25*3.9526e-25 / .01^2)

-1.04e-55

but...  this is a multiple choice question and that answer is not even close to any of the available answers.

Is zero a choice.  1.04x10^-55 is a really small number.

For the second part I assume I need to use Coulombs law

F=kc(q1*q2/r^2)

Where
q1 and q2 are the charges on the particles (in what units? Coulomb's?  How do I find this?)
r is the distance between the objects (in meters)
kc is the electrostatic constant - 8.854e-12

Thanks in advance for any and all advice!

The charge of a proton is about 1.602×10^?19C (you can find this in most chemistry/physics texts under the charge of an electron, which has an equal but opposite charge of a proton).

[Wevie]

Is zero a choice.  1.04x10-55 is a really small number.

No, zero is not a choice.  All of the numbers are really small, but 1.04 is not close to the figure given.  The 10^-55 is close.  I can post the available answers, but I would much rather learn to solve the problem, not just answer the problem.  Do you see any problems with my math or the use of the formula?  Is the formula I am using the correct one to solve this problem?

edit:  didn't originally plan on posting this part, but here are my choices and I can't figure out how to arrive at any of these answers:

A. 1.97e-11
B. 5.80e-54
C. 5.80e-56
D. 5.80e-60

The charge of a proton is about 1.602×10?19C

Thank you.  Sure enough, right there in the text is the charge of an electron and of course the proton will have the opposite charge.  Simple oversight on my part.

[Borek]

Ask your teacher to check his/her math. Nucleus mass is 3.95*10^-25 kg and not 2.95*10^-25 kg.

A typo.

[Wevie]

Ask your teacher to check his/her math. Nucleus mass is 3.95*10-25 kg and not 2.95*10-25 kg.

A typo.

Wow, look at that!  Using 2.95e-25 produces an available answer.  I guess I should have worked the problem backwards to see what mass was used to produce the different answers. 

Thank you so much.  I was starting to question my math, but I felt confident I had worked it out correctly.

Thank you.