Galilean Transformations and Relativistic Physiology

[sfr1]

Hey, I have two separate questions:

1) If one is moving in a car and throws a ball straight up, say out the sun roof, the ball will have zero velocity relative to an observer in the car. Conversely, it will have the velocity of the car to a stationary observer. How does one account for drag forces in this situation? Would the drag force be relativistic and if so, does the fact that the observer in the car sees the ball with zero velocity have significance?

2) I'm guessing there haven't been any experimental data on the subject, but is there any conjecture on the possible effects of relativistic velocities on human physiology? Just curious.

 

[HallsofIvy]

Hey, I have two separate questions:

1) If one is moving in a car and throws a ball straight up, say out the sun roof, the ball will have zero velocity relative to an observer in the car. Conversely, it will have the velocity of the car to a stationary observer. How does one account for drag forces in this situation? Would the drag force be relativistic and if so, does the fact that the observer in the car sees the ball with zero velocity have significance?

If you are admitting drag, then the first part is no longer true. The ball will NOT have zero (horizontal) velocity any more. The observer in the car will see the ball moving backward and the stationary observer will see the ball moving forward but not as fast as the car.

2) I'm guessing there haven't been any experimental data on the subject, but is there any conjecture on the possible effects of relativistic velocities on human physiology? Just curious.

Think about the word "relative". Velocity of any kind can have NO effect on human physiology because the person is not moving relative to himself. If a person is moving at a large fraction of c, relative to an observer, then the observer will see him "compressed" but that is not a "physiological" change. The person himself would see and feel no difference- to him it is the other person who is moving.

 

[Dale]

How does one account for drag forces in this situation? Would the drag force be relativistic and if so, does the fact that the observer in the car sees the ball with zero velocity have significance?

The air simply has a non-zero velocity that causes drag on the ball which is initially at rest. That is essentially how a wind tunnel works.