Real Life Comparison

[herme3]

I have a Compaq Presario X1000 laptop computer, and I was wondering how durable it is. I posted about this in the computer forum, and they said it was something like:

 

vibration: 0.5G at up to 200Hz

shock: 23G faired square wave with velocity changes of up to 508cm/sec

 

I don't know what this means, and I was wondering what a real life comparison would be. None of the people in the computer forum knew, and they said to ask about it here. Does anyone have a comparison? For example, is this like being in the trunk of a car, or falling down stairs? Please let me know. Thanks.

[mezarashi]

I guess the only person who would know is the guy who actual wrote that, but you can conclude a few things. First of all, this is probably referring to your harddisk as the rest of the computer comprises mainly of solid state devices in which gravity simply has negligible effect.

 

First of all, G means gravitational acceleration (precisely 9.8m/second/second on the Earth's surface). Have you ever watched one of those documentaries on military aircraft, saying how they have high maneuverability and can pull 10 G's. That means that they are accelerating 10 times the speed of the gravity. If you were to sit on something that is accelerating upwards at 10G, you would feel 10 times as heavy. And that's VERY heavy. Most people would probably lose conscienceness at less than 10G due to blood not circulating properly.

 

With regards to the computer. You probably now from physics that when something changes velocity, it must undergo acceleration. For example, you drop your laptop off from a 2 story building. It will accelerate at 9.8m/s/s (1 G) to the floor, where it will probably come to zero velocity in a matter of milliseconds. You can calculate this acceleration by doing (change in velocity/ time). Now if this acceleration exceeds that specified (23G = 23*9.8), then you're going to have a problem. In real life, yeah, that would pose a great difficulty because nobody has a millisecond stop watch to time the time of impact during a fall. But then again, neither do the engineers who designed it. Depending on the elasticity of the laptop and the angle of collision, it may or may not survive the drop (although a 2 story drop is obviously going to obliterate it )

 

The vibration component probably refers to oscillatory motion. For example your on a rattling train. The moving features of your harddisk may not be able to accurately function if there is too much rattling. The shock component refers to sudden impact such as a fall. An impact over 23 G would probably cause it permanent internal damage. The faired square wave probably indicates this impulse, although I'm not sure what is meant by the velocity change of 508cm/sec.

 

The engineers of the harddisk can't say for sure that even a 2cm fall won't do damage. Thus the use of Gs. For example, if it happens to land in an awkward angle, it may end up pulling over 23Gs. (consider changing the velocity from 2cm per second to 0cm per second in 0.01 milliseconds = that's 204G's!) So in effect, intuitive judgment is the best means. Take good care of it ^^