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:(adsbygoogle = window.adsbygoogle || []).push({});

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?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Velocity Addition

**Physics Forums | Science Articles, Homework Help, Discussion**