You are on a train traveling east at speed of 16 m/s with respect to the ground.
Your friend is sitting on another train traveling west at 12 m/s. As you walk toward the back of your train at 2.5 m/s, what is your velocity with respect to your friend?
The speed in which the trains are moving away from each other is 28 m/s. Now we get 28 m/s and subtract 2,5 m/s, which is your speed. Answer: 25,5 m/s.
