Calculating Trip Time for Laser Beam to Moon and Back

[Stillwind]

Homework Statement

How long would it take a laser beam to go to the Moon and back if the distance to the Moon is 3.8 x 10^8m?

Homework Equations

a=2d/t^2
d=v1 t + 1/2a t^2

The Attempt at a Solution

a=2d/t^2
9.8m/s(Gravity)=2(7.6x10^8)/t^2
t^2=15.2x10^8/9.8
t= 12453.99698 secs

P.S the answer at the back of the book says 2.6sec

 

[hage567]

Why are you including acceleration? Do you know what the speed of light is?

 

[weatherhead]

photons, being massless, are not affected by gravity... at least not appreciably for your problem