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Homework Help: Converting binding energy of an element to joules

  1. Dec 9, 2012 #1
    Converting binding energy of an element to joules!!

    The binding energy of Mg-24 is 198MeV. What is this value in Joules? Write your answer correct to three significant figures.


    MeV = megaelectron volt
    1 megaelectron volt = 1.60217646 × 10-13 joules
    198 megaelectron volts = 3.17230939 × 10^-11 joules



    198 megaelectron volts = 3.17230939 × 10^-11 joules
    So, the answer should be 3.17E-11. Correct?

    I got the answer wrong on the homework... Could it be because I didn't add the unit to the end of the answer?
    Or am I just completely wrong?
     
  2. jcsd
  3. Dec 9, 2012 #2

    Dick

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    Re: Converting binding energy of an element to joules!!

    The number is correct. But, yeah, an answer in physics without correct units on it is wrong.
     
  4. Dec 11, 2012 #3
    Re: Converting binding energy of an element to joules!!

    I added "Joules" to the end of the answer and submitted the homework again, but I still got the answer wrong. :frown:

    Here are the steps I took to get my answer:

    1. I Googled "198 MeV to joules," and Google's built-in calculator gave me "198 megaelectron volts = 3.17230939 × 10-11 joules" as the result.
    2. Next, I simplified the number to three significant figures and got "3.17E-11".
    3. Finally, I added Joules to the end of my answer, and submitted "3.17E-11 Joules" as my answer.

    Is there another way to solve this problem?
    What did I do wrong?
     
  5. Dec 11, 2012 #4

    haruspex

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    Re: Converting binding energy of an element to joules!!

    Since it asked for the answer in Joules, it should be expecting just a number. But from another post of yours, it looks like the software is poorly written. Try just "J".
     
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