> College of Science > Physics Dept > Tatsu Takeuchi > Special Relativity > Practice Problems > Problem 12
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### Tagging Up in Baseball 2

During a baseball game a fly ball is hit toward left field along the third base line. The left fielder runs backward away from third base and catches the ball at point D on the spacetime diagram. The runner on third base tags up and starts off toward home base at point G on the spacetime diagram.

1. At which spacetime point, labeled A through J, is the third base runner when the left fielder catches the ball at D in the umpire's frame of reference?
2. At which spacetime point, labeled A through J, is the third base runner when the left fielder catches the ball at D in the left fielder's frame of reference?
3. At which spacetime point, labeled A through J, is the third base runner when the left fielder catches the ball at D in the runner's frame of reference after he left third base?
4. In which of the three frames discussed above, namely 1) the umpire's frame of reference, 2) the left fielder's frame of reference, and 3) the runner's frame of reference after he has left third base and is running toward home base, has the runner committed a foul? Explain, referring to the spacetime diagram.
5. If the three observers base their judgments solely on what they see, which of them, if any, would conclude that the runner has committed a foul? Explain, referring to the spacetime diagram.