Let's see ... if Elon's tube train accelerates at the rate his Tesla Model S P85D does 0 to 60, it would take 41 seconds to get up to 760 mph, and the passengers would look like this:
https://www.youtube.com/watch?v=wQHvMU6a0uA
.... and then y'gutt'a slow down and come to a stop
It would be neat if the seats swiveled 180° for the deceleration phase.