Some people think that when an elevator
falls, you may not get hurt by jumping just before it hits the ground. Although
superficially plausible, this view is mistaken.
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1. You can’t stand when the elevator falls free
When an elevator falls free, the inside of
the elevator is weightlessness (zero gravity condition). Strictly speaking, it
is not zero gravity condition, but free falling. But for someone inside the
elevator, it’s akin to weightlessness. In other words, the interior of a
free-falling object is a form of weightlessness.
Using this phenomenon, if it is necessary
to shoot in a weightless state, they shoot in a free-falling airplane at high
altitudes. For example, the movie “Apollo 13 (1995)” and the music video “OK Go - Upside Down & Inside Out” are known to have been filmed using the
technique.
The situation inside the elevator is the
same. As shown in the video, it is very difficult to jump as usual in a
free-fall elevator.
However, if the elevator falls as it rubs against
the wall, or the elevator reaches its terminal velocity because it was located
at a high altitude, the inside of the elevator is not weightlessness. So, in
this case, you may be able to jump in a falling elevator. The following is the
problem on the premise that jumping is possible.
2. You don’t know the timing to jump
As you know, most elevators are opaque on
all sides, including the floor. So, you can’t measure the exact timing to jump.
Although some elevators have transparent
walls, the floor is still opaque. (If the floor is transparent, it is difficult
for people with acrophobia to take the elevator. Therefore, except in special
cases, most elevator floors are opaque.) So, even in this case, you should
measure the timing of the jump by looking at the surrounding terrain rather
than at the bottom, which is also difficult to get the correct timing.
Moreover, the time for the elevator to
reach the floor is very short. For example, it takes only 3 seconds for a free-falling
elevator about 44 meters high to reach the bottom.
Luckily, however, you may succeed in
jumping just before the elevator hits the floor. The following is the problem
on the premise that you have successfully jumped.
3. It doesn’t have much effect.
In fact, the previous item (2. You don’t
know the timing to jump) is incidental. Even if it’s possible to jump, it does
not have much effect.
If you jump in an elevator, the jump will
be in the form of a ‘Sargent jump’ (also known as ‘Vertical jump’ or ‘Vertical
leap’). Although there are variations depending on age or physical ability, the
average Sargent jump test scores are known to be approximately 30 to 40 cm
(11.8 to 15.75 inches). And the world record is known as 63.5 inches (161.29
cm) as of 2016.
The speed of the moment of
jump from this height is calculated as follows.
2aS = V²- Vo²
2gH = V²
V = √2gH
H = 40cm = 0.4m
g = 9.81m/s
∴
V = 2.8m/s = 10.08km/h
The average walking speed of a person is
known as 1.4m/s (5.0 km/h; 3.1 mph; 4.6 ft/s). Thus, 2.8m/s is just a speed
that walks fast. Then let’s find out the speed when the elevator falls from a
height of 40 meters and hits the floor.
mgH = 0.5mV²
V = √2gH
g = 9.81m/s
H = 40m
∴
V = 28.01m/s = 100.83km/h
Compared to the speed when falling, you can
see that the speed is not that high when jumping. When you are in a running
train, you look stationary when you look inside the train but you’re actually
running at the same speed as the train. The same is true of the situation in an
elevator. When the elevator falls at 100km/h, you’re also falling at 100km/h.
Therefore, jumping merely reduces your
falling speed from 100km/h to 90km/h. It’s just the difference between standing
still and walking in the same direction as the car when you’re hit by a car
running at 100km/h.
4.Conclusion
Consequentially, it is not recommended to
jump just before a falling elevator hits the ground.
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