« previous next »
Pages: [1] 2 3 ... 16   Go Down

Author Topic: IGCSE PHYSICS  (Read 23587 times)

Offline @d!_†oX!©

  • SF Master
  • ******
  • Posts: 1268
  • Reputation: 2105
  • Gender: Male
IGCSE PHYSICS
« on: November 06, 2009, 12:54:41 pm »
A bungee jumper of mass 60kg jumps from a bridge tied to an elastic rope which becomes taut after he falls 10m. Consider the jumper when he has fallen another 10m and is traveling at 15m/s.
Work out how much energy is stored in the rope. Take g= 10m/s2 and ignore air resistance.

now i know this is a pretty easy questioon bt i cant get the answer how to do it....the answer is 5250 J....
i did it by subtracting the k.e from the p.e
but why is it so???

guys help plss
Logged
AAL IZZ WELL!!! ;)

Offline ~~~~shreyapril~~~~

  • SF Master
  • ******
  • Posts: 2606
  • Reputation: 2640
  • Gender: Male
  • "Prototype"
Re: IGCSE PHYSICS
« Reply #1 on: November 06, 2009, 01:00:56 pm »
the rope will store PE right??
if not it will have strain energy!!

so if PE then it will be mgh = 60*10*10 = 6000!!

but thatss not the ans so!!
starin energy will be MA = 60*10 = 600!!

but this is also not the ans!!
Logged
Friendship is like peeing on yourself. Everyone can see it but only you get the warm feeling that it gives :D :P :)

Offline @d!_†oX!©

  • SF Master
  • ******
  • Posts: 1268
  • Reputation: 2105
  • Gender: Male
Re: IGCSE PHYSICS
« Reply #2 on: November 06, 2009, 01:01:54 pm »
dude u took the pe wrong cuz it will be 10*20*60
read the ques carefully shrey!!!
Logged
AAL IZZ WELL!!! ;)

Offline ~~~~shreyapril~~~~

  • SF Master
  • ******
  • Posts: 2606
  • Reputation: 2640
  • Gender: Male
  • "Prototype"
Re: IGCSE PHYSICS
« Reply #3 on: November 06, 2009, 01:03:35 pm »
Quote from: @d!_†oX!© on November 06, 2009, 01:01:54 pm
dude u took the pe wrong cuz it will be 10*20*60
read the ques carefully shrey!!!
]
due i have my eyes in place!!!
it says - 10 meters !!
how can you take 20????
Logged
Friendship is like peeing on yourself. Everyone can see it but only you get the warm feeling that it gives :D :P :)

Offline @d!_†oX!©

  • SF Master
  • ******
  • Posts: 1268
  • Reputation: 2105
  • Gender: Male
Re: IGCSE PHYSICS
« Reply #4 on: November 06, 2009, 01:05:08 pm »
Consider the jumper when he has fallen another 10m

can u read this????so 10 + 10 = 20 m


now dont come up with some other excuse to cover up plssss....
Logged
AAL IZZ WELL!!! ;)

Offline ~~~~shreyapril~~~~

  • SF Master
  • ******
  • Posts: 2606
  • Reputation: 2640
  • Gender: Male
  • "Prototype"
Re: IGCSE PHYSICS
« Reply #5 on: November 06, 2009, 01:07:09 pm »
not excuse but i forgot abt it :P :P
we need to subtract PE by KE beacuse it is starin energy right??
and at the time i guess it is PE and just becoming KE so it needs to be subratctd!!!

i guess
lets wait and watch until astar arives!!
Logged
Friendship is like peeing on yourself. Everyone can see it but only you get the warm feeling that it gives :D :P :)

Offline ~~~~shreyapril~~~~

  • SF Master
  • ******
  • Posts: 2606
  • Reputation: 2640
  • Gender: Male
  • "Prototype"
Re: IGCSE PHYSICS
« Reply #6 on: November 06, 2009, 01:18:58 pm »
By the way is this the ans:
60*20*10=12000
0.5*102*60=3000

so 12000-3000 = 9000!!

as you said i have subtracted PE and KE!!
but not the same ans!!
did i do ne mistake!!
i guess i did!!!
Logged
Friendship is like peeing on yourself. Everyone can see it but only you get the warm feeling that it gives :D :P :)

Offline @d!_†oX!©

  • SF Master
  • ******
  • Posts: 1268
  • Reputation: 2105
  • Gender: Male
Re: IGCSE PHYSICS
« Reply #7 on: November 06, 2009, 01:19:52 pm »
yeah u did...the speed is 15 not 10!!!!!!! >:(
Logged
AAL IZZ WELL!!! ;)

Offline ~~~~shreyapril~~~~

  • SF Master
  • ******
  • Posts: 2606
  • Reputation: 2640
  • Gender: Male
  • "Prototype"
Re: IGCSE PHYSICS
« Reply #8 on: November 06, 2009, 01:20:26 pm »
oh yaa!!
og the mistake!!
it must be 0.5*152*60=6750

so it will be 12000-6750=5250..!!

By the way i also have same wuestion why subtarct???
Logged
Friendship is like peeing on yourself. Everyone can see it but only you get the warm feeling that it gives :D :P :)

Offline Ghost Of Highbury

  • O_o_O lala!
  • SF Farseer
  • *******
  • Posts: 4096
  • Reputation: 41428
  • Gender: Male
  • Namaskaram!
Re: IGCSE PHYSICS
« Reply #9 on: November 06, 2009, 01:53:43 pm »
when the jumper is in the middle of his action, the PE stored reduces as it gets converted to KE. Therefore, we subtract the KE from the PE.
i guess this is the answer.
Logged
divine intervention!

Offline @d!_†oX!©

  • SF Master
  • ******
  • Posts: 1268
  • Reputation: 2105
  • Gender: Male
Re: IGCSE PHYSICS
« Reply #10 on: November 06, 2009, 02:06:45 pm »
even i had the same thought in mind...
wt i think is that
elastic energy of the rope+kinetic energy=potential energy
thus, elastic energy=potential -kinetic
i just wanted to confirm it....it'd be gr8 if astar cud say smthng on this....

@shrey dude that's what my question is!!!!!do u like start doing a question sans seeing wat's asked???
Logged
AAL IZZ WELL!!! ;)

Offline ~~~~shreyapril~~~~

  • SF Master
  • ******
  • Posts: 2606
  • Reputation: 2640
  • Gender: Male
  • "Prototype"
Re: IGCSE PHYSICS
« Reply #11 on: November 06, 2009, 02:09:32 pm »
we are asking same questions!!
i did not see and copy!!
By the way your logic has sense aadi!!
Logged
Friendship is like peeing on yourself. Everyone can see it but only you get the warm feeling that it gives :D :P :)

Offline astarmathsandphysics

  • SF Overlord
  • *********
  • Posts: 11271
  • Reputation: 65534
  • Gender: Male
  • Free the exam papers!
Re: IGCSE PHYSICS
« Reply #12 on: November 06, 2009, 03:35:22 pm »
60*10*20-0.5*60*15^2=5250
Logged

Offline Ghost Of Highbury

  • O_o_O lala!
  • SF Farseer
  • *******
  • Posts: 4096
  • Reputation: 41428
  • Gender: Male
  • Namaskaram!
Re: IGCSE PHYSICS
« Reply #13 on: November 06, 2009, 03:39:18 pm »
Quote from: @d!_†oX!© on November 06, 2009, 02:06:45 pm
even i had the same thought in mind...
wt i think is that
elastic energy of the rope+kinetic energy=potential energy
thus, elastic energy=potential -kinetic
i just wanted to confirm it....it'd be gr8 if astar cud say smthng on this....

@shrey dude that's what my question is!!!!!do u like start doing a question sans seeing wat's asked???

y u getting so hyper?
Logged
divine intervention!

Offline @d!_†oX!©

  • SF Master
  • ******
  • Posts: 1268
  • Reputation: 2105
  • Gender: Male
Re: IGCSE PHYSICS
« Reply #14 on: November 07, 2009, 06:01:07 am »
THanks astar!!!
nd aadi when did i get hyper dude???
Logged
AAL IZZ WELL!!! ;)
Pages: [1] 2 3 ... 16   Go Up
« previous next »