Thanks for taking a look. The following question is that is that from a grade 12 academic physics course. 1. The problem statement, all variables and given/known data Scientist Ludwig von Drake, while in his laboratory, measures the half-life of some radioactive material which is in a bomb, approaching with speed v. Donald Duck, who is riding on the bomb, also measures the half-life. His answer is a factor of 2 smaller than Ludwig's. What is the value of v, expressed as a fraction of c? Answer: .87 2. Relevant equations Special relativity equation: t=t0/square root (1-v2/c2) Note: 2 = squared Other: I know there is at least one more I must use but for the life of me don't know what it is. 3. The attempt at a solution First we set V=Drakes. If this is so than Donald's equation must be equal to: t=[t0/square root (1-v2/c2)]/2 Therefore to= 2t[square root (1-v2/c2)] The problem is in equating the equations. They end up cancelling out because one is a direct derivative of the other. This leads me to believe I need at least 1 more equation. It must also be noted that while von Drake may use the special equation of relativity Donald duck cannot (at least this is what I figure). I say this because Donald duck is viewing the half-life from the bomb at rest, meaning he would be more in the realm of inertial frame of reference. What equation i now use knowing that I have no idea. Thanks in Advance guys.