BLOG: Can physics explain why our smartphones prefer to land on their screens when they’re dropped?
We’ve all been there. A stranger has just bumped into you on the tube, you’ve tripped on the street or – most likely – you’re a bit worse for wear on a night out and your expensive new smartphone is removed from the safety of your hands and is tumbling towards the ground.
The panic is eased by a ‘screen-up’ landing, but if it’s landed screen-down, it’s a nervous wait as you pick your phone and see whether cracks have blemished the precious display.
According to Motorola, a phone screen is smashed every two seconds and 29 percent of Brits are using a device with a cracked or shattered display. Whether this is because we’re a clumsy nation or because phone repairs are prohibitively expensive is unknown, but the general consensus is that bad luck is why handsets land on their screen.
Science or luck?
But it might not be luck at all, according to physicist Professor Robert Matthews, whose theory suggests smartphones are more likely to land on their screen because of the way we hold them in our hand.
“People might think it’s just their bad luck when a fumbled phone lands screen-down and smashes. In fact, physics is to blame, making screen-down landings more likely,” he said. “People who are naturally clumsy and often fumble their phones are clearly particularly at risk”.
Essentially, because the devices are held loosely in one hand and fingers placed below the phone’s centre of gravity, it’s at more risk of being dropped and more likely to pivot around our fingers. Once the phone is dropped, it spins at a rate dictated by these forces.
This is where things get a little complicated. The formula (pictured right) is as follows: L is the length of the smartphone, g is the acceleration due to gravity, p = 2δ/L is the “overhang parameter”, δ is the overhang distance, and θ is the angle of the smartphone when it starts its descent.
Because smartphones are so “sleek and smooth” Matthews said they are unlikely to break contact with the fingers before the spin rate is sufficient for a ‘screen up’ landing – potentially explaining why screen down scenarios are more common.
Regardless of how accurate the theory is, at least you can now blame physics – rather than booze or clumsiness – for your broken phone.
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