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I Love Solving Math Questions

 
 
IRFRANK
 
  1  
Reply Tue 31 Dec, 2013 10:05 pm
@Romeo Fabulini,
Quote:
Yes, Pilate proclaimed Jesus "Not guilty", but the snooty priests overuled him..


Years before that the Romans leveled Jerusalem.
0 Replies
 
Romeo Fabulini
 
  1  
Reply Fri 3 Jan, 2014 12:40 am
Okay you maths whizzkids, answer this simple question-
If a high jumper can clear a 7-foot bar on earth, what height would he be able to clear on the moon where the gravity is one-sixth of earths?
It's not exactly a trick question, but you need to know a smidgin about the laws of physics to be able to answer it, I got it from one of Arthur C. Clarkes science books.
dalehileman
 
  0  
Reply Fri 3 Jan, 2014 12:22 pm
@dalehileman,
Yet, what
Nobody at all interested in the math of infinity
0 Replies
 
markr
 
  1  
Reply Fri 3 Jan, 2014 02:45 pm
@Romeo Fabulini,
How high is the jumper's center of mass?
0 Replies
 
Romeo Fabulini
 
  1  
Reply Fri 3 Jan, 2014 04:54 pm
Quote:
Markr asked: How high is the jumper's center of mass?

You're on the right track but no more clues..Smile
Come on you maths eggheads, it's a simple enough question-
If a high-jumper can jump 7 feet on earth, how high would he be able to jump on the moon where the gravity is one-sixth less?
You needn't be exact, just an "about" figure will do.
When all your guesses are in (or if nobody can make a guess within the next few days) I'll scan and post the paragraph from Clarke's book that gives the answer..Smile
Frank Apisa
 
  1  
Reply Fri 3 Jan, 2014 05:24 pm
@Romeo Fabulini,
Romeo Fabulini wrote:

Quote:
Markr asked: How high is the jumper's center of mass?

You're on the right track but no more clues..Smile
Come on you maths eggheads, it's a simple enough question-
If a high-jumper can jump 7 feet on earth, how high would he be able to jump on the moon where the gravity is one-sixth less?
You needn't be exact, just an "about" figure will do.
When all your guesses are in (or if nobody can make a guess within the next few days) I'll scan and post the paragraph from Clarke's book that gives the answer..Smile


My answer: Higher! No need for the about or approximately...I will stick with "higher."
0 Replies
 
tomr
 
  1  
Reply Fri 3 Jan, 2014 11:02 pm
@Romeo Fabulini,
Assume jumper height is 6 ft. Then assume center of mass of jumper is 3 ft.
So center of mass moves 7 -3 ft = 4 ft on Earth. Assume same energy expended on Earth is expended on Moon. (Let hi and hf be the initial and final height on Earth, h'i and h'f are the heights on the moon, m is the mass of the jumper, and g is the acceleration due to Earth's gravity.)

Ee = Em
mg(hf - hi) = m(1/6)g(h'i - h'f)
mg(4) = (1/6)mg(3-h'f)
24 = (h'f - 3)
27 = h'f

The height jumped on the moon would be 27 feet? That is alot. I doubt it would be that much in a space suit.
Romeo Fabulini
 
  1  
Reply Sat 4 Jan, 2014 01:22 pm
@tomr,
Yes you've cracked it at 27 feet which is close enough to Clarkes "around 30 feet", even though the logical answer (trap) would have seemed to be 42 feet!
The key of course is to do with the jumpers centre of gravity..Wink
Here's the bit from AC Clarkes 'Greetings Carbon-Based Bipeds', page 241-

http://i53.photobucket.com/albums/g64/PoorOldSpike/Photos4-newPB/clarkeA_zpsd274befc.jpg~original
0 Replies
 
Ragman
 
  1  
Reply Sun 5 Jan, 2014 11:32 pm
@harpazo,
it figures.
0 Replies
 
harpazo
 
  1  
Reply Mon 14 Oct, 2019 10:52 am
Thank you everyone. I truly appreciate your input.
0 Replies
 
harpazo
 
  1  
Reply Mon 14 Oct, 2019 07:26 pm
Thank you everyone.
0 Replies
 
 

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