Used an online calculator — even a meter falls takes the phone up to 10 MPH. Elsewhere in this thread 20 to 40 MPH was given as the terminal velocity of a phone. FWIW.
Presumably the destructive energy on impact will be proportional to the square of the velocity. Even at 20mph that's 4x the energy, 40mph is 16x the energy.
Realistically I think it's because the way a phone gets damaged is highly dependent on:
- Is it in a case
- Which orientation did it land in
- What surface did it land on
