Ask the experts.... Trivial questions

[Chowlett]

Cool, if somewhat destructive. It looks like they should form a bigger single galaxy afterwards!

[Dauphin]

Not as destructive as you might think.

It looks vicious but that time sequence was sped up from 1/2 billion years to 16 seconds (of action)

[MrFun]

Here is my latest trivial question:


What do they mean by a four-head VCR??

[KrazyHorse]

I would guess that that's the number of read/write magnetic heads the VCR uses...

[Kassiopeia]

Is it true that a fly flying inside a car doesn't get squished to the windows because the car's velocity isn't (over) 1 g? (or was it capital G) If not, then what is the reason?

[KrazyHorse]

The quick answer is that you're talking bollocks.

[KrazyHorse]

Especially neither g nor G are measured in the same units as velocity...

[Buck Birdseed]

Originally posted by Sandman
Why are dodgy medical doctors called 'quacks'?

"Quack" is a short form of the now obsolete "Quacksalver", from C16th Dutch "quack salf", meaning "To Hawk Ointments". Which is what a Quack does, really.

[Lincoln]

I thought of this problem once when I was driving into Salt Lake City. I saw a sign that said "SLC 70 miles" and I was going 70 mph so I figured I would be there in an hour. About 55 miles out of town I saw a sign that said "SLC 55 miles" and a speed limit sign that said "slow to 55 mph". Later when I was about 30 miles out of town the speed limit sign said "30 mph". So I had apparently travelled all of that way for nothing because I was still an hour away from town.

My question is, should I break the speed limit or spend the rest of my life traveling to Salt Lake City?

[KrazyHorse]

Depends on the placement of the signs...

[Kassiopeia]

Okay, I new I was probably skating on thin ice there. But then what the hell is it that keeps the fly from facing a horrible death splattered all over the back window?

[KrazyHorse]

You mean when the car is accelerating?

His ability to flap his wings fast enough to keep up to the increased "gravity" experienced inside the car.

[Kassiopeia]

Increased gravity? As in the pull towards the back of the car? This is starting to make sense, gradually.
But the pull disappears when the car's speed remains constant?

[KrazyHorse]

You've got it. To maintain position in an accelerated frame of reference, the fly has to provide both upwards lift to counteract gravity and forward lift to keep up with the car. Total acceleration needed is the vector sum of g (direction downwards) and acceleration (directed whatever way the car's accelerating).

In a steady-velocity car, the fly feels like it's standing still, since it's in an inertial frame. Note that it's important the car's enclosed, since otherwise the fly also has to deal with a 100 kilometer-an-hour headwind...

[Chowlett]

Does that hold true even if the car does not contain a vacuum? Surely air effects will reduce the force the fly needs to remain stationary.