iPhone 15 Pro’s Altered Inertia Could Give the Impression of Being Lighter Than Its Weight Suggests

By Maggie On Sep 17, 2023

When you pick up the iPhone 15 Pro, one of the first things you’ll likely notice is its significantly lighter weight compared to its predecessor, the iPhone 14 Pro. Apple attributed this weight reduction to the switch from a stainless steel frame to a titanium one. However, this feeling of lightness hides more than meets the eye, as revealed by the insightful analysis of Dr. Dear LeanCrew’s blog.

For reference, the iPhone 15 Pro weighs 187 grams, which is 9% less than the 206 grams of the iPhone 14 Pro. During the product launch, Apple focused on emphasizing the lighter feel made possible by the transition to titanium. Indeed, early adopters such as MacRumors’ Dan Barbera have confirmed this perception, noting how remarkably light the device feels in the hand. A study by Dr. However, Dranga digs deeper and suggests that the iPhone 15 Pro maybe even lighter thanks to the change in moment of inertia than its actual weight reduction.

Now you might be wondering what exactly is moment of inertia is. In physics, it is a basic concept that measures an object’s resistance to rotational motion. It is affected by both the mass of the object and how that mass is distributed. Crucially, as the mass is placed further from the object’s axis of rotation, the moment of inertia increases. For everyday objects like smartphones, this feature plays a significant role in how it feels in our hands.

Apple’s decision to switch from stainless steel to titanium for the iPhone 15 Pro’s outer band is key to this transformation. Much of the phone’s weight reduction is concentrated around its outer edges. Analysis of Dr. Dranga suggests that by concentrating mass primarily on the perimeter, Apple has achieved a reduction in the phone’s moment of inertia that goes beyond what would be expected from weight reduction alone.

This decrease, which is more significant than the weight reduction itself, contributes to the iPhone 15 Pro being easier to handle and improves the overall perception of lightness. Put simply, the phone isn’t just lighter; its design ensures that its mass is strategically distributed to reduce resistance to rotational motion. Result? A device that feels more agile and nimble and provides an even greater feeling of lightness.

To put this into perspective, the analysis estimates that the moment of inertia for the iPhone 15 Pro has been reduced by a substantial 14-15%. This means that this phone is not only lighter; its design choices ensure that it resists rotational movement less strongly, creating a device that is remarkably light and responsive in the palm of your hand.