NOVA Online (click here for NOVA home)
Time Travel
Site Map

Think Like Einstein
Part 1: Adding Velocities

Animation of train example

We begin with a basic concept—one that sets the scene...

You're on a train that's moving forward at 50 mph. You throw a ball in the direction that the train is moving. Relative to you and the train, the ball leaves your hand travelling at 20 mph.

Question: From the point of view of someone standing alongside the tracks, how fast is the ball moving?
  1. 20mph
  2. 30mph
  3. 50mph
  4. 70mph

Sagan on Time Travel | Traveling Through Time
Timespeak | Think Like Einstein | Resources
Teacher's Guide | Transcript | Site Map

Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule
About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print
PBS Online | NOVA Online | WGBH

© | Updated November 2000