3 ms·

Once it reaches its maximum velocity the altitude doesnt really matter. However I dont know how to calculate that maximum velocity and the minimum required alti

• ciupicri 3y ago
  What about the heat? If the fall is longer won't the phone heat up more?
  • JKCalhoun 3y ago
    And yet the air rushing past provides cooling.... Maybe you're thinking about an iPhone de-orbiting from ISS. That would be a different story.
  • simcop2387 3y ago
    Nope, at the altitude planes are at, the atmosphere is much much colder than at ground level. Along with that the terminal velocity of the phone is going to be under the speed of sound so there won't really be any meaningful compression going on to heat up the air around it like you get with a descent from space. That heating essentially happens (this is simplified) because a space craft is going much faster than it's terminal velocity at the given altitudes it's passing through so it compresses the air below it, heating it just like you'd expect from the ideal gas law. It happens to be that it heats it so much that it makes a super-heated plasma so you end up with what looks like fire (not sure if there's actual combustion happening, but i wouldn't be shocked) surrounding the craft. That's also why once it's slowed down by the friction and air resistance, the plasma dissipates and is no longer a problem for re-entry. Now if we were to launch the phone at several times the speed of sound we could probably get the same thing to happen but I'm doubtful that a phone could survive the acceleration in the first place.
  • eptcyka 3y ago
    At the terminal velocity of an iPhone, the air passing through will do more to cool it than to heat it up due to friction.
  • MadnessASAP 3y ago
    It would actually get quite cold, at 16000' you can expect the air to be well below 0 (pick your units, it's fuckin cold). The only time heating becomes an issue is at supersonic velocities and is due more to compression of the atmosphere against the object then actual friction.
    • arghwhat 3y ago
      > pick your units Kelvin In all seriousness, it can be down to -70 degrees Celsius.
• solomatov 3y ago
  Drag (air friction) is proportional to the square of velocity. If you know aerodynamic properties of iphone, you could find a value of velocity where drag is equal to gravitational force, at which point the speed doesn't change. You could use it as an approximation of the speed at which iphone hits the ground.
• 9front 3y ago
  “It was still pretty clean, no scratches on it, sitting under a bush and it didn’t have a screenlock on it,” from the article. No information how big the bush was but it cushioned the landing.
• mannykannot 3y ago
  After its initial acceleration, the phone probably decelerated as its altitude decreased. The air density at 5 Km is about 0.6 of that at sea level. As drag is proportional to the air density and the square of the velocity, I think that implies the phone would reach the ground at a speed ~3/4 of its peak velocity (putting aside the admittedly significant issue of its orientation and rotation throughout the fall.)