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So THAT'S why phone screens always smash: Formula reveals height and spin rate cause a dropped phone to land face down up to 60% of the time

Mobiles suffer from the same forces as toast that lands butter-side down
A physicist has examined the factors that predict how a phone will land
Texting with one hand is a particular risk as it causes the phone to pivot
The research was conducted for mobile manufacturer Motorola

Published: 08:05 EST, 26 November 2015 | Updated: 09:43 EST, 26 November 2015

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Watching your mobile phone slip from your hand to land on the floor with a crunch is a stomach-churning moment made worse by turning it over to discover the screen has shattered.

Now a physicist believes he has unravelled why mobile phones seem so prone to landing screen side down when they are dropped.

The explanation, it seems, is similar to the reason why toast tends to land butter side down.

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A physicist has worked out the factors that help to predict whether a mobile phone will land on its screen when dropped. These include where on its centre of gravity it is being held, the height it is dropped from and the length of the phone, along with the material it is made from (illustrated)

Professor Robert Matthews, a physicist at Aston University, claims that because of the way mobile phones are held when in use, they tend to spin when dropped.

However, due to the height at which they are held, they rarely manage to spin enough to ensure they land screen-side up.

Indeed, the slippery, glossy finish that is used to make modern mobile phones so attractive could also be part of the problem.

Professor Matthews has developed a formula that he claims can predict how a mobile phone will land when dropped. 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

An estimated 29 per cent of people are currently using a mobile phone with a cracked or shattered screen. The increased use of glass touch screen phones has meant the devices are more prone to damage when dropped

WHY A PHONE NEARLY ALWAYS LANDS FACE DOWN

When a phone is held loosely in one hand with the user's fingers below the phone's centre of gravity - which often occurs when texting one handed – this makes the phone more likely to pivot around the fingers.

As it leaves the hand it spins at a rate dictated by a variety of forces including gravity, the angle it is being held at, the size of the phone and the height at which it is dropped from.

Physicist Professor Robert Matthews developed an equation that estimates the rate at which a smartphone will spin as it falls.

It shows that due to the height at which phones are typically held, they rarely manage to spin enough to ensure they land screen-side up.

The material they are made from can increase the risk of it landing on its screen from 50 per cent to more than 60 per cent.

This is because the smoother a phone is, the more likely it will break contact with the fingers before it achieves a spin rate.

Professor Matthews, who was funded by Motorola to conduct the work, said the way a phone is held and the material it is made from can increase the risk of it landing on its screen from 50 per cent to more than 60 per cent.

'People might think it's just their bad luck when a fumbled phone lands screen-down and smashes,' he said.

'In fact, physics is to blame, making screen-down landings more likely.

'People who are naturally clumsy and often fumble their phones are clearly particularly at risk.'

Professor Matthews found that if the phone is held loosely in one hand with the user's fingers below the phone's centre of gravity - which often occurs when texting one handed – this makes the phone more likely to pivot around the fingers.

As it leaves the hand it spins at a rate dictated by a variety of forces acting on the phone including gravity, the angle it is being held at, the size of the phone and the height at which it is dropped from.

He has developed an equation that he says estimates the rate at which a smartphone will spin as it falls towards the ground.

The material the phone is made from can also play a role.

The smoother it is, the more likely it will break contact with the fingers before it achieves a spin rate that will ensure it lands screen side up.

Motorola claims to have created a 'clumsy proof' phone that is guaranteed not to shatter when it is dropped (pictured). The Moto X Force has a display made from five layers to absorb the shock of an imPact

An estimated 29 per cent of people currently have a mobile phone with a cracked or shattered screen, according to a survey conducted by Motorola.

The mobile manufacturer claims to have produced the world's first 'clusmy-proof' phone with a screen that it says is guaranteed not to shatter.

The Moto X Force has a display made of five layers designed to absorb the shock from an impact.

WHY YOUR TOAST ALWAYS SEEMS TO LAND BUTTER SIDE DOWN

It is a sticky issue that has plagued scientists – and breakfast tables – for decades.

But researchers claim to have found the definitive answer as to why a piece of toast always seems to fall buttered side down.

Apparently, it’s all to do with the height of the table. They claim that after it topples off the edge, the toast only has time to perform a half-somersault before it lands.

As the side which has been buttered is naturally facing upwards, that’s the side which ends up on the floor.

To confirm the theory, food expert Professor Chris Smith and his team dropped 100 slices of toast from a table at Manchester MET University. The table was two and a half feet high.

In 81 per cent of cases, the buttered side made contact with the floor.