# eli5 – how does the shock resist for phone cases work?

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Phone cases such as spigen, uag, casetify, promotes their cases as those shock absorbant cases. How does it work? And is it shock resist if the phone bounces more?

In: 4

There’s an expression in engineering: if you do not bend, then it means you break. The case on a phone is designed to give that bend on impact to cushion the fall. When we’re talking a fraction of a second impact, even a fraction of a second springy effect is massive for surviving.

Onto an example with fake numbers with fake units, to help understand *why*.

Shock is measured in G-forces, which can be calculated as the speed change of the phone over the amount of time it happens. If a surface is very hard and the phone’s shell is hard (which it normally is), then the impact of landing will bring the phone from “moving” to “stopped” in a very short period of time, like 0.002 seconds. From a height of ~5 feet or so, we’ll call it “fallen 5 feet” of speed divided by 0.002 is some number of G’s. The exact number doesn’t matter.

If an object bounces, it will go from “stopped” to “moving” again but I’m only interested in the physics up to the moment it stops at the bottom of its fall. Any bounce couldn’t be higher than the number of Gs from the falling impact. Also I am making up numbers here, please do not take them literally.

If the case it’s covered of is a bit squishy, then on impact the case squishes itself before it reaches maximum compression (squash) when the falling phone has actually come to a complete stop. Let’s say that process takes about 0.02 seconds to happen. Same distance, but 10x the amount of time, means 1/10th the G forces experienced by the phone. That seriously increases its ability to survive.

The shock resistance of phone cases is typically achieved through the use of materials that are able to absorb shock and reduce the amount of force that is transmitted to the phone itself. Some phone cases use soft materials, such as silicone or rubber, that are able to compress and absorb shock when the phone is dropped. Other phone cases use hard materials, such as polycarbonate or plastic, that are able to spread out the force of the impact over a larger area, thereby reducing the amount of force that is transmitted to the phone. Some phone cases also have additional features, such as raised edges or corner protectors, that help to further absorb shock and protect the phone from damage.