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Prof Works Out Formula As To Why Smartphones Land On Their Screen When Dropped

Prof Works Out Formula As To Why Smartphones Land On Their Screen When Dropped
Prof Works Out Formula As To Why Smartphones Land On Their Screen When Dropped

Have you ever been through that moment when you have dropped your phone and then having to wait agonising seconds as you turn your smartphone over to discover if the screen has shattered.

The explanation, it seems, is similar to the reason why toast tends to land butter side down. Compounding this is the increased use of glass touch screen phones has meant the devices are more prone to damage when dropped.

A physicist who has been working with the Lenovo owned Company Motorola 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.

Professor Robert Matthews, a physicist at Aston University in the USA, 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.

Now 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 = 2?/L is the ‘overhang parameter’, ? is the overhang distance, and ? is the angle of the smartphone when it starts its descent.

He claims that when a smart 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.

Professor Matthews equation 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.

You guess it.

 Now 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.