# How fast does light travel in 1 ft?

by dan001
Tags: light, travel
 P: 2 Hello everyone, I was wondering if anyone could help solve my problem... ...How much time in seconds (or milleseconds) would light travel in 1ft? (assuming that it was traveling in a vacuum.) I spent 2 and a half hours yesterday trying to solve this problem, but without much luck. I remember back in school, I would know how to do this kind of stuff, but now...well, you know. If anyone knows the answer to this problem (and if possible, a formula), I would much apreciate it.
 P: 2,051 speed = distance / time. Use google calculator. Welcome to PF.
 Emeritus Sci Advisor PF Gold P: 11,155 How much time to cover 300,000,000 meters (that's about 1,000,000,000 ft)? So, how much time to cover 1 ft?
P: 2
How fast does light travel in 1 ft?

 Quote by cesiumfrog speed = distance / time. Use google calculator. Welcome to PF.

Wow, I don't believe how I could forget something so simple.

Thanks anyways for reminding me.
HW Helper
PF Gold
P: 4,137
 Quote by Gokul43201 How much time to cover 300,000,000 meters (that's about 1,000,000,000 ft)?
um... wait, gimme just a ....
P: 2,046
 Quote by robphy gimme just a ....
...and a teeny, tiny bit more.
 Sci Advisor HW Helper P: 8,953 Light travels at 1 foot / atto-fortnight, everyone knows that.
P: 1,345
 Quote by mgb_phys Light travels at 1 foot / atto-fortnight, everyone knows that.
You are a nerd among nerds
 Sci Advisor HW Helper P: 8,953 No, a real nerd uses c = 1.8 terafurlongs per fortnight
Math
Emeritus
Thanks
PF Gold
P: 39,565
 Quote by mgb_phys No, a real nerd uses c = 1.8 terafurlongs per fortnight
And watch them ponys run!
HW Helper
Thanks
P: 25,228
 Quote by mgb_phys No, a real nerd uses c = 1.8 terafurlongs per fortnight
Um, what's that in planck units?
 Sci Advisor HW Helper P: 8,953 That would be a good homework question, what is planck's constant in the furlong/firkin/fortnight system.
HW Helper
Thanks
P: 25,228
 Quote by mgb_phys That would be a good homework question, what is planck's constant in the furlong/firkin/fortnight system.
Mines a trick question. In planck units c=1, hbar=1 and G=1. Yours is harder. What's the mass unit in the firkin system? Stones, right?
HW Helper
PF Gold
P: 4,137
 Quote by mgb_phys That would be a good homework question, what is planck's constant in the furlong/firkin/fortnight system.
Using dimensional analysis,
h is in Joule-seconds or kg*(m/s)^2*s = kg*m^2/s

Although http://en.wikipedia.org/wiki/FFF_System says that firkin is a mass,
However, since it is used with water (whose density is about 1000 kg/m^3), we have an expression for the mass in kg of a firkin of water http://www.google.com/search?q=kg+in...+kg%2Fm%5E3%29

So, since google has a problem with numerical constants in the unit conversion,

h / 1 000 = 4.8405995 × 10-34 (firkin * (kg / (m^3)) * (furlong^2)) / fortnight

or
h = 4.8405995 × 10^(-34) (firkin of water) * (furlong^2) / fortnight