Elevator Free Fall?

If I were in an elevator that was free falling, would it help at all if I perfectly timed a jump .. Page 1 of 2
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If I were in an elevator that was free falling, would it help at
all if I perfectly timed a jump before it hit the ground floor?
Would anything help the situation?
Asked by: Ron Cassford
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Answer
In a state of free fall, both you and the elevator are weightless, and
jointly approaching the bottom of the shaft at the same high velocity.
You are in a similar position to an astronaut floating around in his
capsule or spaceship, unable to stand or get a secure footing on
anything without recourse to magnetic boots and/or ropes and
handles to pull against.
Therefore, so far as jumping is concerned, it may be possible to
make some very rough inefectual attempt, but remember in a state
of free fall, you do not have the huge mass of the Earth to steady
you and push against only, by comparison, the minute mass of the
elevator car. You may in your weightless struggles succeed in
pushing yourself away from the floor of the elevator and bumping on
the roof but your original velocity will be little, if at all, diminished,
certainly not enough to save you, and impact with the roof of the
elevator will restore your velocity. Remember also that astronaut has
days, months, to push and pull himself around, you in the elevator
have only seconds.
Disregarding any resistance due to friction or air pressure which
would destroy the concept of free fall, after little more than 4
seconds your velocity is about 40 metres per second or say in the
region of 90 miles per hour and increasing every instant. If you are
say a person weighing 80 kilograms then your momentum P=MV,
that is P = (80Kg) times ( velocity 40 metres per second) ie 3200
kilogram meters per sec. This increases every instant because of the
acceleration due to Gravity which is 9.8 meters per second every
second. Your problem is somehow to get rid of this building
momentum before you do so at the bottom of the shaft. You certainly
cannot reduce your mass of 80 Kg.The human body is not capable,
even under normal circumstances of jumping upwards at 40 meters
per second or 90 miles per hour if you have it in mind to reduce your
velocity to zero by moving at a similar speed in the opposite
direction. As indicated above jumping in the conventional sense of the
word is not possible. A sudden jump a split second before you and the
elevator impact the ground, were this posible, would be no good, for
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If I were in an elevator that was free falling, would it help at all if I perfectly timed a jump .. Page 2 of 2
you would similarly crush yourself by the abrupt onset of the required
force in the opposite direction, which is similar to what happens if you
hit the bottom of the shaft.
What you need is space, in which you can gradually reduce your
velocity, and an elevator which has no roof. Retro rockets strapped to
you waist could work provided their counterthrust in the opposite
direction to your fall did not have too rapid an onset.. Your downward
plunge would be gradually arrested whilst the lift fell away from you ,
Similarly a parachute, if it could be made to deploy and work within
the confines of the lift shaft could save you, but remember things are
happening very quickly and time and adequate space for arresting
devices are not on your side.
In point of fact being in the elevator is practically irrelevant, for the
position is almost exactly the same as if you had jumped into the
shaft, you can readily imagine the hoplessness of the situation and
the maximum distance you could fall and survive, a few meters
perhaps. Thus lifts in free fall and at high velocity are to be
avoided, as death is almost certain.
Answered by: Don Bird, Berkshire UK
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