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Will your new MacBook crash to the ground without MagSafe? (Yes.)

Glenn Fleishman | March 13, 2015
Perhaps we should have read it as an omen that the MagSafe 2 adapter for older, original MagSafe connectors was listed as discontinued on the Apple Store in the U.S. and Canada last week. It's back in stock this week, but MagSafe's future in new Mac laptops is uncertain with the revelation of the single-port MacBook. With just a USB-C connection for power, data, and display, MagSafe may be on its way to sing with the choir invisible.

Perhaps we should have read it as an omen that the MagSafe 2 adapter for older, original MagSafe connectors was listed as discontinued on the Apple Store in the U.S. and Canada last week. It's back in stock this week, but MagSafe's future in new Mac laptops is uncertain with the revelation of the single-port MacBook. With just a USB-C connection for power, data, and display, MagSafe may be on its way to sing with the choir invisible.

That's a shame because Apple has retrained people of all ages, and perhaps some animals, to not worry about Mac laptop power cables. Go ahead! Stand on it, trip over it, yank it — the force of the smallest effort pulls it free.

To quote Apple's MagSafe patent:

...the surface area of two magnetically attracted halves determines the number of magnetic flux lines and therefore the holding force between them because the holding force is proportional to the contact area between the two magnetically attracted halves...

What they said.

A USB Type C (or USB-C) cable has no such advantage. It has two distinct differences: first, a USB-C male end, such as the tip of a cable, is plugged into a port, very much like larger and deeper Type A and Type B USB connections.

Second, while MagSafe was optimized to help with "non-axial" force — any direction except straight out — the USB-C style plug and jack suffer the worst from that. As astrophysicist Katie Mack said, "The genius of the MagSafe connector is that if you apply a force in any other direction it breaks the magnetic seal very easily, and then there's virtually no force required to remove the connector entirely."

But how likely is a cord-tripper to yank a new MacBook off a surface versus the USB-C cable coming out first? My calculations, vetted by Mack and a variety of engineers, show it's almost certain the MacBook will move a bit or a lot unless all your stars perfectly align.

Hold on! Some math's coming, but it's worth it.

There's a disturbance in the force

The USB Implementors Forum specifies precisely how much force should be required to pull a USB-C cable free, measured in newtons (N), which is the force required to accelerate one kilogram (kg) of mass at 1 meter per second squared (1m/s2). Because acceleration is an exponential function, an object travelling at rest that is moved at 1m/s2 traverses 0.5m (1.6 feet) in the first second, 2m by the second second, and 4.5m by the third second.

The USB group says a fresh connector should require 8N to 20N of extraction force. After 10,000 connection cycles, no fewer than 6N should be required. (To compare with something you're already familiar with, USB Type A connectors sold as parts typically note a minimum 10N force for extraction.)

 

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