Ahh, I understand what I did wrong now. I overlooked the fact that the spaceship only has kinetic energy while it is travelling. I solved for KE, then plugged that back into E=mc2. Rearranging for m I got the answer of 1.0x104 kg, which was correct. Thank you very much. Also if you don't mind...
Homework Statement
A spaceship is powered by a matter-antimatter reactor. Suppose you have a 23000-metric-ton spaceship and wish to accelerate it to 0.03 c. What is the total mass of matter and anti matter required, assuming a 100 % efficient engine.
Homework Equations
Really not sure about...