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For example: 1,1-dimethyl-3-(1,1,3-trimethylbutyl)cyclooctane why do you start numbering the "dimethyl" group as one instead of the "butyl" group? I am confused because from what I understand: "Number the longest chain beginning with the end nearest a branch." Arent both these branches?

Ok I undertand that you start writing the name with group with the most carbons, but I still don't understand how do you know where to start numbering if you have 2 of the exact same groups at two different spots. Like if you have two ethyl groups. As far as having the smallest numbers, for example in a ring you could have the groups at the 1,3 positions or the 3,1 positions depending on how you number the ring. In this case the substituents are the same. Also, do you always number clockwise?

When naming cycloalkanes under the IUPAC system, and numbering the main carbon chain (or in this case ring), where do you start numbering the carbons for reference? I know that you are supposed to number them according to according to alphabetical alkyl group. Like if you have a arene with a methyl and ethyl group you would start with the ethyl and go clockwise with the numbering. However, when it is a cycloalkane and the subsituents are both ethyl groups at two differnt spots, where you start the numbering? Thanks for replies and sorry if this sounds confusing.

Thank you! That is exactly right. After finding "c," all I had to do was sum the forces in the x diretion to find "T" (tension) . Then plug tension into the sum the forces in the y direction, and then solve for mass. F(x) = c + (-Tsin30) = 0 F(y) = -mg + (T cos30) = 0 m = (Tcos30)/g It was simple, but the fundamental part I previously overlooked was the fact that the objects were not moving therfore, sum of the forces in the x and y direction equal zero. Thanks to all who helped!

I am not sure about T, but if c is the force on the Y sphere, can't we use coulomb's law? F = {Kc* lq1l *lq2l}/r^2 (Kc times absolute value of test charge times absolute value of source charge divided by r squared) constant: Kc = 9.0x10^9 Nm^2C^-2 BTW...thanks for the replies so far

What do you put in for tension "T" (for this particular problem)? From what I can see in your diagram you used the length of the string (.3m) for T. Is that correct?

YES, that is exactly right. First mistake I made was I used tan instaed of sin (thanks). Now since I can calulate the Coulomb's force on Y, can I relate it to F=mg? I am concerned that maybe I didn't consider all the forces in the X and Y direction, like tension. Then again when I think about "mg" it seems it only has do with the Y direction.

Yes, sorry the diagram is not so good.

Anyone know about Coulomb's law, mass, distance?

Anyone? Maybe someone can tell me if I am to determine the mass, do I only consider the forces in the x-direction. Or the sum of the forces in both directions. I would think F=mg would be enough to relate the coulmb force sphere Y "feels" and mass of the sphere. However I think maybe the tension should be considered. Someone please help.

Can someone tell me if this is right? 30 cm = 0.3 m (0.3m)(tan 30) = 0.17 m (distance) F= (9.0x10^9N.m^2C^-2)(3.00 C)(6.00 C)/ (0.17m^2) = 5.6e12 N (coulomb's law)^^ 1N = 1 kg*m/s^2 F=mg m = F/g m = (5.6e12 kg*m/s^2)/(9.8 m/s^2) = 5.7e11 kg

Ok maybe someone know how distance, coulomb force, and mass is related?

A student performs Coulomb's classic experiment. Shes adds Y coulomb of positive charge to a small metal sphere that is suspended by a thread. Shes adds X coulomb of positive charge to a small metal sphere that is held on a glass rod. She positions the X coulomb sphere as indicated in the diagram and because like charges repel eachother the Y coulomb sphere is pushed out to the right. Calculate the mass of the Y coulomb spere. hint:It is bigger than you might guess. angle=30 degrees X = 3 Y = 6 l l 30 cm l l O O X Y

Hi everyone. My name is Mike and I currently a student at USF. Glad to part of the forums.