Amuse yourselves - Grin with cat attached — LiveJournal
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Amuse yourselves Jun. 13th, 2002 01:04 pm

From: adjectivemarcus
Date: June 13th, 2002 - 05:20 am (Link)
70% - not bad as I last read any physics stuff fourteen years ago!
From: sashajwolf
Date: June 13th, 2002 - 05:23 am (Link)
From: booklectic
Date: June 13th, 2002 - 05:32 am (Link)
40%. Hmmm. I used to be good at physics, but admittedly I was 15 at the time.
From: ajva
Date: June 13th, 2002 - 05:33 am (Link)

Respectable enough, I s'pose. :o)

physics moment

From: ajva
Date: June 13th, 2002 - 05:40 am (Link)
Actually I had a "physics moment" the other day when Stef & I were watching a film and there was a scene where this bloke fell through a glass roof to the ground below. There was a shot looking upwards at the falling man and broken glass, and Mr. Unpronounceable decried the scene for questionable physics, as surely the man would fall faster than the broken glass?

Cue much bouncing up and down from me and ranting about Galileo. I was rather chuffed with myself, truth to tell; it's been a while.

Stef claimed to remember this from school physics - after I'd told him about it. A likely story...

Re: physics moment

From: feanelwa
Date: June 13th, 2002 - 07:57 am (Link)
no, he *would* fall faster, as he'd have an initial downwards velocity from falling onto the roof in the first place, and this velocity would be increased by g so that his velocity t seconds after hitting the glass would be v + gt. the glass around him on the other hand would have been stationary when he hit it and would just have velocity gt. so theoretically he'd land and then be showered by the broken glass.

however the pieces that he landed directly on would gain velocity v when he hit them - then when they reached v they would travel at v + gt as well.

so the scene would go:
man hits roof and feels glass he fell on press on his back.
man falls through air at v + gt and can't feel glass on his back while he's falling
man hits ground and feels glass on back again
man is showered by glass that was around the bit he fell on.

and an observer on the ground would see the man falling towards the camera with broken glass between him and the camera, and then also see him land and be showered by glass.
otherwise they couldn't have got the shot...

the moral: don't fall through a glass roof.
oh yeah sorry if anyone's afraid of heights :S

Re: physics moment

From: babysimon
Date: June 13th, 2002 - 08:04 am (Link)
You're assuming the man loses no velocity during the impact. I think this is quite dubious.

Re: physics moment

From: ajva
Date: June 13th, 2002 - 08:10 am (Link)
Well, wouldn't he lose some velocity, but not all? So the point is still a good one...

Re: physics moment

From: feanelwa
Date: June 13th, 2002 - 10:35 am (Link)
depends how thick the glass is. if he came to a complete stop and *then* it broke, then yes, the glass would fall at the same speed as him, but otherwise it'd still be going a tiny bit slower.

Re: physics moment

From: djm4
Date: June 13th, 2002 - 12:37 pm (Link)
Depends. The atmospheric drag on falling shards of glass may well be higher than that on a body. This would be more noticeable the further he fell, of course.
From: babysimon
Date: June 13th, 2002 - 05:34 am (Link)
92.5%. Grrrr. Stupid car-crash.
From: ciphergoth
Date: June 13th, 2002 - 06:12 am (Link)
Me too (though I got the car crash right). I'm not embarrassed by my wrong answers on clouds and what hands measure, but I should have thought about the voltage question more carefully.
From: robinbloke
Date: June 13th, 2002 - 05:36 am (Link)
60% how embarrasing.
From: wechsler
Date: June 13th, 2002 - 05:38 am (Link)
85% FWIW


From: nevla
Date: June 13th, 2002 - 07:08 am (Link)
And i thought i was good at Physics.
I blame work, it's sapping all my intelligence...
From: olithered
Date: June 13th, 2002 - 07:54 am (Link)
From: feanelwa
Date: June 13th, 2002 - 07:58 am (Link)
my god i should be drunker.
From: potatoprint
Date: June 13th, 2002 - 08:30 am (Link)
50%, I'm stunned. I didn't do GCSE physics, but I would have got a higher mark than I got after 2 years of chemistry.
From: djm4
Date: June 13th, 2002 - 11:47 pm (Link)
95%. I wasn't sure what they meant by 'like' in the 'atoms are like planetary systems' question, and I forgot that voltage wasn't a force.
From: kyte
Date: June 14th, 2002 - 02:17 am (Link)
Around 67% here (took it yesterday, forgot). I should probably top up my physics know-how - I dropped it at school aged 13. The stuff I've looked at more recently has mostly been the kind of stuff they don't ask about (e.g. relativity, quantum theory etc).