- #1
ranjit_k
- 5
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To explain weightlessness to my students, I use the analogy of a falling elevator (lift) as folows - if we stand on weighing scales in an elevator and the elevator cable snaps, the scales will show zero since they are falling to the ground at the same acceleration as us, therefore registering no reaction force.
However, the sensation of being in a lift hurtling to the ground (as anyone who has been on those free-fall rides at amusement parks knows) is surely not that of floating in the air as we see astronauts doing. The difference seems to be that a falling lift has only a vertical velocity while an orbiting shuttle has a horizontal (tangential) velocity also.
In other words, if my falling lift were to have a horizontal initial velocity component also (ie, were thrown as a projectile parallel to the ground), and that component were imagined to be made larger and larger until it covered a horizontal distance equal to the circumference of the Earth in the time it took to 'fall' to the ground (which it never would), then we would experience in the lift the same 'floating' sensation that the astronauts undergo, because the lift would be in orbit (at the small height above ground from which it had when thrown).
Is that a correct way of putting it? Isn't the orbitting shuttle really only a falling lift thrown with a large enough horizontal velocity?
Ranjit
However, the sensation of being in a lift hurtling to the ground (as anyone who has been on those free-fall rides at amusement parks knows) is surely not that of floating in the air as we see astronauts doing. The difference seems to be that a falling lift has only a vertical velocity while an orbiting shuttle has a horizontal (tangential) velocity also.
In other words, if my falling lift were to have a horizontal initial velocity component also (ie, were thrown as a projectile parallel to the ground), and that component were imagined to be made larger and larger until it covered a horizontal distance equal to the circumference of the Earth in the time it took to 'fall' to the ground (which it never would), then we would experience in the lift the same 'floating' sensation that the astronauts undergo, because the lift would be in orbit (at the small height above ground from which it had when thrown).
Is that a correct way of putting it? Isn't the orbitting shuttle really only a falling lift thrown with a large enough horizontal velocity?
Ranjit