A Physics question: come come, all jc,poly,sec, univ people!

• vito_corleone

  3 Sep 05, 00:47

  sorry i was from arts..i didn't take science subjects.
• Cristiano@Red_Devils.com

  3 Sep 05, 01:23

  Originally posted by Cindyfeh:

  Assuming both the chin up bars start at sea level. Theoretically, it will be easier to do chin-ups at the 5 m high bar because you are further away from the center of the earth. The further away from the center of the earth, the less you weight and thus easier to do chin-ups. But because the difference is only 4.5m, the decrease in weight is not noticable at the human senses level, thus physiologically, you feel that you exert the same strenght at both 2m and 5m.

  So far looking thru all the answers and explainations, i think this one is the closest to the model answer.
  
  Just like to add a point.. for the case of doing chin up, a person is doing work against his own WEIGHT. And WEIGHT = MASS X g, where g stands for gravitational pull or gravitational acceleration (unit is ms-2) The mass of the person is constant, but the value of g is not a constant at different heights with respect to sea level. It is inversely proportional to the distance of the body from the centre of earth, which means the further the body is away from the centre of the earth, the smaller the value of g, which means the lower the WEIGHT of the person.
  
  Looking at a more exagerated scenario, compare a person doing chin up at a 2m bar and a person doing chin up in outer space. Definitely the person at outer space would have a easier job because he is almost weightless in outer space due to the low value of g. However if u compare a person doing chin up on a 2m bar against a 5m bar, the difference in g is negligible, hence not much difference in the person's WEIGHT, and hence not much difference in the effort required to do the chin up.
• Mr Fugue

  3 Sep 05, 08:38

  Originally posted by Xcert:

  ya lor..like U invert urself...hands on the bar...down...chin over bar...then cannot straighten arm...become flex-arm-hang-inverted....
  
  as if U < 0.5m tall...

  wah, you talk so much................I was merely hinting how female servicemen do chin-ups.
• coffeeortea

  3 Sep 05, 08:43

  Originally posted by Mr Fugue:

  when I eat fillet o fish at mac (bedok), will I get the same cholestrol if I had eaten at mac (orchard)??

  hhahahaaha, let me add on to the analogies.
  
  if i have sex on a tree with a female, or if i have sex on an airplane with a female, has her virginity been lost?
• tIfosI

  3 Sep 05, 10:27

  It's the same. Whether u r 2 m or 5 m above the ground, you still weigh the same and the distance of of one chin up remains the same.
  
  Discounting relavistic effects.
  
  Energy = mass * gravity * delta distance
  
  Of course that is discounting energy exerted to reach to the higher ground to start doing chin ups.
• Icemoon

  3 Sep 05, 11:29

  Originally posted by tIfosI:

  It's the same. Whether u r 2 m or 5 m above the ground, you still weigh the same and the distance of of one chin up remains the same.
  
  Discounting relavistic effects.
  
  Energy = mass * gravity * delta distance

  theoretically cannot weigh the same right? 'cos the g will still be different due to distance from Earth's centre.
  
  
• Icemoon

  3 Sep 05, 11:30

  after all the discussion .. I believe it is more beneficial to do chin up in Tibet.
• Jinsenlim

  3 Sep 05, 13:01

  Hi,
  
  There is a difference if you are having chin up are 5m off the ground.
  The gravitational is the same. mass*gravity. But the potential energy
  is definety higher. mgh. or maybe i wrong. hee hee
• usck

  3 Sep 05, 13:01

  u all can complie all these theory and named it as Sgforums's Chinup theory. go for NOBEL Prize!!
• tIfosI

  3 Sep 05, 15:26

  Originally posted by Icemoon:

  theoretically cannot weigh the same right? 'cos the g will still be different due to distance from Earth's centre.
  
  

  Ya, that's what I meant by discounting relavistic effect, you will weigh slightly less as you move away from from massive object.
• nightzip

  4 Sep 05, 01:03

  try thinking in steps:
  
  1). arms hanging on the bar.
  2). arms flexing to pull your chin above the bar.
  3). arms relaxing/or free-fall of your hand to the base-level.
  
  then imagine in your head the difference between 2m and 5m.
  
  
• the.raven

  4 Sep 05, 01:12

  Originally posted by nightzip:

  Let's say you do chin-up.
  
  Can anyone tell me if everything thing else remains the same, if you were to do 12 chin-ups at a bar 2m high and if you were to do the 12 chin-ups at a bar 5m high, will you exert the same force/strength?
  
  Thanks.

  yes you will.
• teekh

  4 Sep 05, 01:51

  negligibe diff...
  
  What sia...use GMm/r^2 ar? haha
• hisoka

  4 Sep 05, 02:03

  Originally posted by teekh:

  negligibe diff...
  
  What sia...use GMm/r^2 ar? haha

  yeah lor neglibie difference but still got lah must teach pple properly if not wait get scolded next time how?
• the.raven

  4 Sep 05, 10:22

  Originally posted by vito_corleone:

  sorry i was from arts..i didn't take science subjects.

  feeble artsies.