Oscillations typo? (21.79)

1. Oct 4, 2015

Calpalned

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

2. Relevant equations
$r=0.15-0.05cos(\omega t)$ $\omega = \sqrt {\frac{k}{m}}$
$\vec{E}=\frac{Qk}{r^2}$
3. The attempt at a solution
In my end result, I got the same thing as above, but with 10^5 in the numerator. According to the solutions guide, the final answer is a simplification of $\frac{2.7*10^4}{(0.15-0.05cos(13.92t))^2}$ Did I make a mistake or did the textbook? Thank you.

2. Oct 5, 2015

Staff: Mentor

Hi Calpalned. Is this a problem easily solved in your head, or is there some working that you have forgotten to attach?

3. Oct 5, 2015

Calpalned

I solved it already, It just want to check if it's 10^5 or 10^7