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Hypothetical rescue in a falling elevator
Can I save myself in a falling elevator by jumping just before impact?
I hope that no one will have to experience this situation because it will not be possible to jump in a falling elevator — I will explain the situation where we do not take into account the air resistance. If an elevator falls, the elevator will move with the acceleration of gravity g (we won’t count air resistance) ...
Lift forces on an aerobatic aircraft
How is it possible for an airplane to fly horizontally during aerobatics, even when it is upside down? The lift on the wings should pull him down and not up…
It is true that the plane takes off due to the geometry of the wings. The upper part is more bulging than the lower part and therefore the air flows at a higher speed around the upper part of the wing than the lower part. And it follows from Bernoulli’s equation that the higher the velocity of the fluid, the lower the pressure at a given location ...
Creation of vacuum by explosion
An explosion (e.g. a nuclear bomb) creates a pressure wave, i.e. air spreads outwards from the epicenter. Does this mean that a vacuum is created at the site after the explosion?
Yes, that’s right. A pressure wave is typically created by an explosion (it doesn’t matter what the source is) compressing the surrounding air. Because air is a flexible environment, this compression will spread further. You can try something similar yourself — just push water in a pool (or in a bath or pond) with your palm ...
