Date: Wed, 24 Aug 2005 04:56:34 +1000 From: Peter Jeremy <PeterJeremy@optushome.com.au> To: Borja Marcos <borjamar@sarenet.es> Cc: freebsd-hackers@freebsd.org Subject: Re: IBM Active Protection System Approach Message-ID: <20050823185634.GE37107@cirb503493.alcatel.com.au> In-Reply-To: <34E57F6C-EDF8-4E51-86AC-863109217B85@sarenet.es> References: <200508221720.j7MHKpNb022773@peedub.jennejohn.org> <430B11B0.20702@pacific.net.sg> <200508232155.02444.doconnor@gsoft.com.au> <34E57F6C-EDF8-4E51-86AC-863109217B85@sarenet.es>
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On Tue, 2005-Aug-23 15:37:49 +0200, Borja Marcos wrote: >>mmm.. There is a static 1G force on the laptop while it is on your >>desk. When >>it falls it goes to 0G as it is in free fall. >> >>Still.. "delta G == park laptop heads" :) > > It's not a "force meter", but an acelerometer. It measures >acceleration. If the computer is sitting on your desk, as it has >already been said, it detects nothing. When falling, the acceleration >is 1 G, ie, 9.8 m/s^2 Actually, it's the other way round. The accelerometer is detecting acceleration within the frame of reference of your laptop. When sitting on your desk (or holding it stationary in your hand), the accelerometer will detect a static 1G acceleration. Whilst your laptop is falling, the accelerometer reads 0G (neglecting air friction) because your whole laptop is accelerating. It might be easier to think of the accelerometer measuring the force exerted by a fixed mass sitting on your laptop. -- Peter Jeremy
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