Weird gravity on mobile

It’s so strange that I have a box which sets the simulate physics to true and enables the gravity and i place It up in the air above the landscape,when i play in editor,it falls down normally,but when i run it on mobile including iOS(iPhone6plus iPad air1/2)Android(ASTC ATC),the box falls more slowly than in editor or in mobile preview.i haven’t changed the default gravity settings.Why that happens?Thanks a lot!

Edit:I found that the box falls more quickly in metal than in es2,but still slower than on PC
Edit2:After further investigation,I have found that this issue may have something to do with the frame rate,on Metal,my game runs almost at 30~50fps,so the falling are fast,but on es2,usually 20~30fps,so the box falls more slowly…
But why that happens?In that case,I have to optimize the game to extremely smoothing in order to get that normal falling speed?