Search: To find out answers to a specific question, copy a representative sentence from the question and paste the sentence in the search form and search it. The results show the most related questions and yours may be in there. Feel free to share LeiAcademy.org with other teachers and students.  
To discourage spam, only registered users can ask questions.

Welcome to Physics Homework and Study Help, where you can ask questions and receive help on learning physics. We currently focus on helping questions in introductory level college physics and high school AP Physics courses.
To discourage spam, only registered users can ask questions.

Facebook Twitter Google

Welcome to Physics Homework Help Page on LeiAcademy.org

Feel free to ask a question and also answer questions others asked. Answering others' questions can in turn help one's own understanding and build a warm healthy community for learning. The followings list a few things that might be helpful for you to effectively obtain help on specific physics homework or practice problems.  

Search: To find out answers to a specific questions, copy a representative sentence from the question and paste the whole sentence in the search form and search it. The results will show the most related questions and yours may be in there

Browse: To find out what have been discussed, asked or answered, put in a few key words in the search form and search for related questions, answers, and or solutions. Or you can click the related tags or other tabs to find useful information there. 

You can also write professional-looking equations using Latex codes (see details here).

This site is hosted on LeiAcademy.org, which will continue to add new resources for learning. Feel free to share this with other teachers and students.  

A molecule of DNA

0 votes
303 views

A molecule of DNA (deoxyribonucleic acid) is 2.10 µm long. The ends of the molecule become singly ionized: negative on one end, positive on the other. The helical molecule acts like a spring and compresses 1.29% upon becoming charged. Determine the effective spring constant of the molecule.

I keep getting within 10% and can't figure out where I'm going wrong.

asked Jan 12, 2014 in Others by anonymous

1 Answer

0 votes

The charge of an electron is 1.6*10-19C.  "singly ionized" means the charge both ends of the molecule is e (1.6*10-19C). the "r" is the length of a DNA molecule. According to Coulomb equation F=kQ1Q2/r^2, we got the force.Then, F=kx, where x is given (the molecule is compressed 1.29%).

 

If it is with 10%, just keep trying with 2 sigfigs.

p.s. I'm just a student but I got it right:) If you are done with Question 11 Plz help me! thanks! 

 

answered Jan 12, 2014 by Will_White (1,010 points)
That's what I did but it's still wrong. Must be a webassign problem
Actually I just tried for 4 times and then I got it. (my calculator shows it should be 2.454e-9, then I tried 2.45, 2.4, and finally I tried 2.5e-9, it was right).
BTW, webassign sucks.
web counter
...