Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

iPhone 15 Pro Likely Feels Even Lighter Than It Really Is Due to Inertia Change

MacRumors

MacRumors

macrumors bot
Original poster
Apr 12, 2001
63,764
31,216


The iPhone 15 Pro likely feels considerably lighter than the iPhone 14 Pro, not just due to the switch from stainless steel to titanium, but also a change to the device's moment of inertia, according to calculations by Dr. Drang's LeanCrew blog.

iPhone-15-Pro-Internal-Chassis.jpg

The iPhone 15 Pro weighs 187g, a 9% reduction of the iPhone 14 Pro's 206g weight. During its announcement, Apple highlighted that the new lightweight feel is facilitated by switching from a stainless steel frame to titanium. Those who have already spent some time with the iPhone 15 Pro, including MacRumors' Dan Barbera, have noted just how much lighter the device feels in the hand. Yet new analysis suggests that the iPhone 15 Pro likely feels even lighter than its actual weight reduction due to a change of its moment of inertia.

The moment of inertia, a fundamental concept in physics, measures an object's resistance to rotational motion. Its value is determined by both the amount of mass an object has and how that mass is distributed. Crucially, the further away mass is positioned from an object's axis of rotation, the greater the moment of inertia. Thus, for commonly handled objects like smartphones, this resistance to rotation plays a significant role in how weighty or light they feel during daily use.

Apple's shift from stainless steel to titanium for the iPhone 15 Pro's outer band is pivotal in this change since a substantial portion of the phone's weight reduction is localized at its outer edges. Dr. Drang's analysis suggests that by minimizing mass predominantly at the perimeter, Apple achieved a reduction in the phone's moment of inertia that is more significant than would be expected from the sheer weight decrease alone.

This reduction, which is more than the mass reduction, would make the iPhone 15 Pro easier to turn, and that may add to the impression that it's significantly lighter than the 14 Pro.

[...]

Reducing the mass at the perimeter, which the change from stainless steel to titanium has done, has definitely reduced the moment of inertia more than a uniform reduction in mass would have. And that will make the 15 Pro easier to manipulate and will contribute—at least somewhat—to the impression of lightness.
Click to expand...

Based on an analysis of the new phones' dimensions and assuming the mass reduction is mostly around the phone's perimeter, the moment of inertia for the iPhone 15 Pro is estimated to be reduced by 14–15%. Overall this means that the iPhone 15 Pro doesn't just weigh less; its design ensures that its mass is distributed in a manner that makes it resist rotational motion less strongly. This results in a device that feels more agile and nimble, giving an amplified impression of lightness.

Article Link: iPhone 15 Pro Likely Feels Even Lighter Than It Really Is Due to Inertia Change
 
Article Link
https://www.macrumors.com/2023/09/17/iphone-15-pro-likely-feels-lighter-than-it-really/
  • Like
  • Love
Reactions: DiscoDude77, Pinkyyy 💜🍎, 640K and 6 others
T

theluggage

macrumors 604
Jul 29, 2011
7,545
7,467
phill85 said:
This seems like a huge stretch, not gonna lie
Click to expand...
The "moment of inertia" stuff is correct, but does make it sound a bit technical. Thinking in terms of "centre of gravity" and leverage is probably easier.

Think of a ball of lead that fits in your palm, so all the weight is supported by your palm.

Now think of the same weight of lead beaten out into a foot-long stick, that you hold by one end, so the centre of gravity is some distance from your palm and is trying to bend your wrist.

For a phone, concentrating the weight in the area that is usually supported by the palm of your hand (typically the centre of the lower 2/3) should make it more comfortable to hold.

Edit - note: Just to be clear, I'm not saying "centre of gravity" is the same thing as "moment of inertia" - this is a just simplified example of how distribution of mass affects how "heavy" something feels.
 
Last edited:
  • Like
Reactions: Pinkyyy 💜🍎, kanon14, 640K and 11 others
xraydoc

xraydoc

Contributor
Oct 9, 2005
10,810
5,280
192.168.1.1
My wife's standard iPhone 13 feels huge compared to my 13 mini. I've preordered the iPhone 15 Pro, so I'm glad it will be as light as possible (and have a tighter center of gravity).
 
izyreal

izyreal

macrumors regular
Sep 26, 2012
219
814
USA
phill85 said:
This seems like a huge stretch, not gonna lie
Click to expand...
It’s real because it’s physics. Removing weight from the edges of the phone makes the phone easier to twist.

You can prove it to yourself by sitting on a spinning chair and holding weights out to the side. Then ask someone to spin you. Then take the weights away and have them spin you again. They will tell you it was much easier to spin you without the weights.

 
  • Like
  • Love
Reactions: Pinkyyy 💜🍎, caribbeanblue, CarlJ and 18 others
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom