1. The problem statement, all variables and given/known data In space near earth, about 3.84*10^21 photons are incident per square meter. On average, the momentum of a photon is 1.3*10^-27. Assume we have a 1205 kg spaceship, and a square sail that is 26.3m wide. How fast could the ship be travelling after 21 days? 2. Relevant equations F*Δt=m*v 3. The attempt at a solution I started out by finding the force the photons would have on 1 m^2 and then multplied that by 26.3 to get the force on the sail [itex] (1.30*10^-27)(*3.84*10^+21)*(26.3^2) [/itex] and got .00345 N Since F=ma, I divided that by 1205 to get 2.865*10^-6 I then took 21 days and changed it to 1814400 s. So i multiplied 2.865*10^-6 by1814400 to get 5.19914 m/s. Did i go wrong somewhere cause the computer says im wrong.