Basic physics: why an iPhone survived a fall from an airplane but can shatter if it falls out of your hands

The incident with the Alaska Airlines Boeing 737 Max 9, which had its door fall off at an altitude of 4.9 kilometers, was a sensation in itself, and was covered by all the media. But then something else surprising happened that did not go unnoticed: an iPhone fell out of the same plane and survived the crash. Although this sounds unlikely and quite impressive, the usual laws of physics, plus a little luck, fully predict such an outcome.

Rhett Alleyne, a physicist at Southeastern Louisiana University (USA), explained how this miracle happened and why it makes no difference if such smartphone falls from 100 meters or several kilometers.

The durability of modern phones can be partly explained by the fact that smartphone screens have been improved over the years. However, they still shatter simply by falling out of clumsy hands, so hearing about a successful drop from almost 5 kilometers is a miracle.

According to Alleyne's calculations, a smartphone falling from a height of 1.2 meters will hit the ground at a speed of about 16 kilometers per hour. At the same time, a fall from a height of 4.9 kilometers would result in a speed of 96 kilometers per hour. Obviously, there is some kind of disproportionate increase in speed to height. Still, there is a scientific explanation for this.

A physicist explained that after a certain number of meters, it doesn't matter how high an object falls because it stops accelerating at a certain point.

This happens because the resistance of the air pushing the object upwards will reach the same value as the force of the earth's gravity pulling the object down. Thus, the object will stop accelerating and will fall at a constant (or finite) speed. It all depends on the weight of the object itself.

If we talk about the iPhone 11, for example, Alleyne estimates that the smartphone will stop accelerating after about 100 meters of fall. So it doesn't matter if you drop the smartphone from 4.9 kilometers or 100 meters: its final speed will be the same.

But it's not just about the height of the fall, it's also about stopping. That is, the survival of the phone will largely depend on what it lands on. From a physical point of view, the landing material is important because it will change the duration of the impact.

"The longer the impact lasts, the lesser its force," Alleyne explained.

"For example, dropping your phone on a pillow will cause it to compress and prolong the moment of impact. But a fall on concrete will already have a sad result due to the lack of any cushioning: the impact will be very short as the phone will slow down almost all at once and will have a lot of force.

In the case of the iPhone that fell out of the plane, it was most likely the luck factor that saved the phone. The published photos show that the smartphone was found on the road in an area with a lot of tall bushes.

Alleyne suggests that they became that cushion.

"Every time it touches different parts of the bush, it slows down a little bit. The impact time will be longer than if you dropped your phone on the kitchen floor," the scientist explained.

For his part, Colin Wilkinson, director of the Center for Glass Innovation at Alfred University (USA), also said that the way the phone fell is important. According to him, if a piece of glass falls flat and lands flat, "it shouldn't break no matter what," as the force of the fall will be distributed throughout the glass.

But if the smartphone falls at an angle or hits a pebble, there is a chance that a very small point will be subjected to a lot of pressure and the screen may crack.

This happens because there are small defects in the glass that are potential points "where cracks can start."

Various scientists are currently working to remove these defects.

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