Dont buy HDD's or other fraglie things from play.com

[Behemoth]

Rather than a photo here is a description of the second time with the plastic bag. The HDD was
in an anti static bag placed loose inside the plastic bag, there was no packing of any kind
not unless you call the invoice packing. The plastic bag wasn't folded up either.

If it doesnt work this time I am getting a refund and going to scan... those boys know how to wrap
things up properly.

Agree with you on that one, bought a 320 gig hard drive from them for my laptop last month and it arrived in so much bubble wrap, I don't think I've seen a hard drive turn up quite so well packed !

[KidChameleon]

If it doesnt work this time I am getting a refund and going to scan... those boys know how to wrap
things up properly.

I bought a cakebox of DVDs and a few small cables last week and it was all packaged in a million layers of bubble wrap.

I once bought a laptop hard drive from Amazon and it came in one of their normal DVD/book cardboard wraps. Better than 0.5mm of plastic, I suppose. It worked ok but I was always a bit unsure of it. The trouble with general etailers is that they tend to be packed by people who don't really know a lot about all the products, so they might not know how fragile hard drives are. Having said that, they should have some guidelines on what kind of packaging to use.

[bsodmike]

I stand corrected. Quite surprised at that actually.

The reason I did that analysis in the first place was Omega were marketing their "Mission to Mars" Speedmaster X33 with a shock-resistance rating of 10,000 g's. I read many blog articles, reviews and even forum discussions where people were like "that's incredible!" etc.

It's all to do with the impulse of a force. An intuitive conclusion does not consider the duration and distance the object travels during it's deceleration from impact velocity to rest. A regular floor would be pretty hard, and as you can see, about 100-times to 1,000-times more g's are experienced than one would typically expect

[Rave]

From the above analysis it can be seen that dropping an object (with a mass of 150 grammes) from a height of 1 m (~3 ft) will cause it to experience a shock of ~99,999 g whilst generating ~45 hp of power, if the distance travelled during impact is ~0.01 mm [i.e. a granite floor, or similar hard surface

That assumes that the falling object is infinitely hard though, doesn't it? In practice if you drop a hard disk 1m onto a granite floor you will dent it. If that dent is 1mm or more, which it most likely will be, all the parts of the hard disk that did not directly impact the floor will experience a deceleration of <1000g.

[bsodmike]

That assumes that the falling object is infinitely hard though, doesn't it? In practice if you drop a hard disk 1m onto a granite floor you will dent it. If that dent is 1mm or more, which it most likely will be, all the parts of the hard disk that did not directly impact the floor will experience a deceleration of <1000g.

Yup, that would be true but it's not going to dent more than say at most a cm or so. They are pretty tough tbh, especially if it falls on an edge. Still, good point.

[Rave]

Not even a cm, I wouldn't have thought, but in your original calculation (the workings of which are entirely correct as far as I could be bothered to examine it) you specify that the deceleration happens over .01mm, resulting in a deceleration of ~100,000g. If the deceleration happens over 1mm, then obviously the average will only be 1/100th of that, I.E. 1000g. Now I don't doubt that in the real world it's perfectly possible to subject objects to decelerative forces of well over 1000g, I just don't think dropping a hard disk from 1m would do it.

As an aside, apparently the highest decelerative force a human has experienced and survived was 110g, though since this was a racing car in 1977 I'm not quite sure how they established its impact speed and the precise distance over which it stopped with such accuracy. More recent telemetry has calculated that drivers of Indycars have survived ~70g hitting walls.

[kalniel]

Not to mention the bounce..

[Funkstar]

And surely any packaging around the drive, no matter how meagre is going to have an effect. For instance, if you drop an OEM 2.5" drive through a letter box in just the anti-static bag it comes in, it's most likely to fall vertically (as in the drive oriented vertically) and land on a corner on the bag. Put this inside even a standard paper envelope is going to cushion it quite a lot.

in the real world, I still don't think you are going to get 1000G from a posted hard drive hitting a floor. Not unless you are really unlucky.

[bsodmike]

Not even a cm, I wouldn't have thought...

I was being generous, especially for side-on collision

Not even a cm, I wouldn't have thought, but in your original calculation (the workings of which are entirely correct as far as I could be bothered to examine it) you specify that the deceleration happens over .01mm, resulting in a deceleration of ~100,000g.

The distance of 0.01 mm was simply the result of assuming a 'hard' surface like granite.

If the deceleration happens over 1mm, then obviously the average will only be 1/100th of that, I.E. 1000g.

That's a great point, once again; the "crumpling" distance. I will include this addition to my next revision; email me your 'real world' details so I may include them under the credits section

As an aside, apparently the highest decelerative force a human has experienced and survived was 110g, though since this was a racing car in 1977 I'm not quite sure how they established its impact speed and the precise distance over which it stopped with such accuracy. More recent telemetry has calculated that drivers of Indycars have survived ~70g hitting walls.

That's certainly nice to know

[TooNice]

Okay, I hope you physics people can answer the question that has bugged forever. I am not sure if I've asked on this forum, but if I did then either I did not get a reply, or I forgot the answer - sorry

Suppose you are on a small crashing plane. Now assume that you are outside, crouched on one of the wing, and somehow managed to not fall off it. Thanks to your l33t sense of timing, you know when to leap so that your entire body is in the air the instant the plane crashes (no explosion).

1. Would there be a downward pressure capable of preventing you from successfully making that leap (perhaps all the 'Gs')?

2. If not, what is the difference between the above scenario and leaping off the wing of a plane at standstill?

Sorry for going OT, but I think I am in good hands on this thread

[Funkstar]

You body is still going at whatever speed the plane was travelling at, just because you jump, you don't loose all that kinetic energy. Yu are still going to hit the ground going very fast in a pretty uncontrollable way.

I predict death.

[TooNice]

I thought of that, but if the downward energy is that great, wouldn't you just fail to leap at all? Or do you succeed in your jump and *suddenly* get pulled down at the full speed of the plane even though a fraction of a second ago you induced an upward energy? And suppose you do somehow manage to get your feet off the plane with the jump, would you get pulled down right away (millimetres off), or can you get a reasonable jump before being pulled down and effectively get crushed?

(Sorry again for the stupidity of the question, but I stopped physics long before I could figure this up logically on my own )

[jim]

1. Would there be a downward pressure capable of preventing you from successfully making that leap (perhaps all the 'Gs')?

2. If not, what is the difference between the above scenario and leaping off the wing of a plane at standstill?

As for the first, I wouldn't think there's any particular downward force that would prevent the jump, but as you mentioned it would be impossible to stay on in the first place as a result of the lateral force of drag... that same lateral force would equally make it impossible to jump I would imagine. Making similar assumptions to you, that this person has superhuman strength and electromagnetic boots, they feasibly could leap off the wing.

However, as Funkstar said, if the plane is hurtling to the ground at 300 mph, it's not just the wing travelling at that speed. So is the hull, the carpets, the seats, and hence so is the passenger. If you're in a car crash, when it hits a solid object you lunge forward at 30mph or whatever - the seatbelt saves your life by giving your chest a very long impact time. It's got something to do with momentum (I can't remember exactly what, but it's a similar idea to what Rave was discussing with the hard-drive - the longer it takes, the lower the impact force). On the wing of a plane, or just above the wing of a plane, you don't have any restraint, so you continue moving at 300mph.

The effect would be exactly the same as being fired out of a cannon at 300mph, pointing towards the ground, starting at whatever height you decided to jump at. The only possible benefit would be if it was very high up, as you would slow down to your terminal velocity, which would be lower than the terminal velocity of a plane. Effectively you would be jumping without a parachute, giving you a vague chance of survival. However, given the circumstances you suggested, the result of a 300mph impact with the ground is going to be splat.

[jim]

I thought of that, but if the downward energy is that great, wouldn't you just fail to leap at all? Or do you succeed in your jump and *suddenly* get pulled down at the full speed of the plane even though a fraction of a second ago you induced an upward energy? And suppose you do somehow manage to get your feet off the plane with the jump, would you get pulled down right away (millimetres off), or can you get a reasonable jump before being pulled down and effectively get crushed?

There isn't really "downward energy" apart from gravity - both you and the plane are falling at the speed previously suggested.

Let's suppose you're falling at 300mph. You, with your superhuman strength to resist drag and electromagnetic boots to hold yourself to the wing, decide to jump. This gives you an upward acceleration of 1m/s^2. Consequently, you accelerate upwards, reducing your downwards speed from 300mph to 299mph, lifting you just above the plane wing which is still travelling at 300mph.

Now that you're not attached to the plane wing, your speed will also drop to terminal velocity where drag = weight, so you'll move even further away from the plane. Then we move onto the splat scenario.

I only did physics to A-level, but I think that's fairly accurate.

[Funkstar]

Yup, Snooty's second reply was what I was going to say as well.

When you jump standing on the ground, you oppose gravity and accelerate up to a point and then accelerate back down again. You have the same effect when jumping off the wing, it's just have to add in the velocity of you falling with the plain in the first place. It doesn't get cancelled out magically.

[mikerr]

Suppose you are on a small crashing plane. Now assume that you are outside, crouched on one of the wing, and somehow managed to not fall off it.

You'd be (very slightly) better off letting go of the plane, as your terminal velocity would be 100mph, a lot less than the streamlined plane's of 200+ mph ...


However:

Stewardess Survives 33,000ft Crash!
http://www.super70s.com/super70s/tec...ugoslav%29.asp
http://en.wikipedia.org/wiki/JAT_Flight_367
http://en.wikipedia.org/wiki/Free_fall#Surviving_falls

Seems you want to land on snow to stand any chance...