I'm trying to figure this problem out, and think it's not that hard, but am having trouble acquiring the answer. Here is the problem: You and a friend decide to "hitch" a ride in the mailcar of a train heading to Green Bay (due north). Halfway there, your friend asks you for a sandwich out of your backpack. As you throw the sandwich to him, it travels at a speed of 0.20c relative to himself and due north. If the train is moving at 0.50c and a cop sitting stationary at the railroad tracks observes your throw, what speed would he clock the sandwich at if he pointed his speed gun at it? So, I use the equation for relative velocity in relativity: v = (u+w)(1 + uw/c^2) From this equation, I simply plug in the numbers, u = 0.50c and w = 0.20c, then I obtain 2.31E8 m/s . However, this seems kind of strange since the velocity observed by the cop should be less than .7c and 2.31E8 is greater than .7c . Am I doing something wrong?