String length

1. Jan 26, 2015

moriheru

I am actually quite sure I have it right but my book would then be wrong so I have posted my problem here to see if I didn't do a embarassing mistake in arithmetics.
1. The problem statement, all variables and given/known data
"Show that the energy equivalent of the length 10-18cm of a large extra dimension is roughly 20TeV"
-Zwiebach 2004

2. Relevant equations

ħ=c=1
ħc≈200MeVx10-15m
ls=√α
mc2=ħc/ l
3. The attempt at a solution
Just some simple reforming first:

E=mc2=ħc/l

then substituting numbers and converting units:

10-18cm=10-16m

E=200MeVx10-15 m / 10-16 m

= 200 MeVx10x10

=20000 MeV=2x1010 eV

,where Zwiebach says it schould be roughly 20 Tev 10^12 eV.

Thanks for any clarifiactions

2. Jan 26, 2015

Orodruin

Staff Emeritus
Is 0.01 cm = 1 m?

3. Jan 26, 2015

I see.