Here's the question you clicked on:

## heena Group Title ok they had given pendulum done 100 oscillation its amplitude reduced to 1/3 of initial value. what will be its amplitude if it completes 200 oscillation 2 years ago 2 years ago

• This Question is Closed
1. JamesJ Group Title

100 oscillations in what time period?

2. heena Group Title

dont solve just tell me ur vies dat how will u suppose to handle this ques plz plz but dont solve

3. heena Group Title

*view they didnt give time period so we can assume it constant??

4. JamesJ Group Title

I still don't understand the question. Is it this: "In a given time period a pendulum completes 100 oscillations. "Then the pendulum has its amplitude decreased by 1/3 and it completes in the same time period 200 oscillations." If so, what's the question here.

5. heena Group Title

no they didnt said anything abu time period even i m asking can we assume it constant

6. JamesJ Group Title

What is true about a pendulum is that if you increase the angle of maximum oscillation more than about 10 degrees, the period of the pendulum increases. The reason for that is in calculating the standard period of pendulum, we use a small angle approximation $\sin\theta \approx \theta$ which only holds for small angles $$\theta$$. The wikipedia article has good animation of what happens when $$\theta$$ gets large and there you can see the period increases. http://en.wikipedia.org/wiki/Pendulum#Period_of_oscillation This would explain the effect described in this set up.

7. heena Group Title

but james my ques how i m gonna solve it ? any hint or idea even i m trying hit and try but u can tell ur one too that it might like dis?

8. heena Group Title

u guys have any idea?

9. heena Group Title

it is saying that when pendulum completes its 100 oscilation its amplitude reduced to 1/3 of its inital means 2/3 is remain of apmlitude i guess and then they are asking if it completes 200 oscilation than what will be the value of amplitude

10. hosein Group Title

i think amplitude decrease

11. heena Group Title

i need a value too.. :P

12. JamesJ Group Title

Oh, I see. Precisely what is the amplitude, in angular terms. Use the first couple of terms of this expansion:

13. heena Group Title

god.. u r kidding james by showin me dat short formula rit ...

14. heena Group Title

i thinks in that i m not getting they are squaring or wat?? inside the bracket?

15. Shayaan_Mustafa Group Title

hello. i am back.

16. hosein Group Title

with 100 oscillation amp 1/3 decrease so with 200 oscillation again decrease 1/3 im not sure

17. JamesJ Group Title

You know that T decreases by a factor of a 1/2. Use that formula to find what value of theta_0 will make that happen.

18. Shayaan_Mustafa Group Title

may i help here? May i could do something?

19. heena Group Title

yea solve diss ques

20. Shayaan_Mustafa Group Title

ok wait. let me analyze.

21. heena Group Title

i wasted 15mins in this ques yar

22. heena Group Title

plz quick

23. hosein Group Title

james formula is correct?

24. heena Group Title

yea but unable to aplly a i nvr heard abu dat one

25. hosein Group Title

james formula abu period of oscillation,not amplitude

26. Shayaan_Mustafa Group Title

now what i understand. BUT THIS QUESTION LOOKS INCOMPLETE. look here first calculate time period using T=1/f T=1/100 T=0.01sec

27. heena Group Title

guys i need the ans 1/9 nw think ow can we get

28. heena Group Title

f=? y u put ocilation??

29. hosein Group Title

idont understand u'r sentence?

30. heena Group Title

i mean the ans of this ques is 1/9 now just hit and try to get this ans

31. hosein Group Title

how can you got it?

32. heena Group Title

no i dont got dat i had ans key :) and my ans is not matching dats why i ask for help..

33. Shayaan_Mustafa Group Title

now use the displacement equation, y=Asinwt where w is the frequency. y=(1/3) sin(100*0.01) y=(1/3)(0.0174) y=0.005m now use this displacement as, 0.005=Asin(200*0.01) 0.005=A(0.0348) A=0.143 :( is this wrong?

34. Shayaan_Mustafa Group Title

there is no other way to do it. so it tried my best. and result is before you. :((

35. heena Group Title

i want to cry.. :"( )............ )............................ god if this kind of ques coming on exam i m gonna dead

36. Shayaan_Mustafa Group Title

what is exact answer?

37. Shayaan_Mustafa Group Title

i am sure it is right.

38. heena Group Title

1/9 i meantion it too

39. Shayaan_Mustafa Group Title

1/9 is equals to 0.1. so it is right. may be.

40. heena Group Title

yes u r rit u got it congo.........

41. Shayaan_Mustafa Group Title

congo?

42. heena Group Title

but in ur equation asinwt here t is time not time period

43. JamesJ Group Title

Heena. Let's try this one last time. Write out the complete question in your best English.

44. heena Group Title

lolz.. ok

45. hosein Group Title

ithink shayan answer is wrong.

46. heena Group Title

when an osicllator completes 100 oscilation then its amplitude reduced to 1/3 of its initial value of amplitude.what will be its amplitude if an osicllator completes 200 oscilation

47. JamesJ Group Title

This question is still very ambiguous. It means either * The time periods for the 100 and 200 oscillations are different and just a distraction. The amplitude is 3rd of what it is and that's the end of it. * We're talking about a pendulum and the period of oscillation changes. In which case we need to use the formula I wrote above * Something else.

48. Shayaan_Mustafa Group Title

i know. when i said it is true. it may be wrong. i just tried. although i am an electronics engineer not a theoritical physicist.

49. heena Group Title

guys had a idea leave it even i already wasted 30 mins in this ques better to leave this i ll ask my lecturer dont worry

50. Shayaan_Mustafa Group Title

yeah, good idea.

51. heena Group Title

thnQ for being here for help .. i always gave good ideas u knw gyan guru :P

52. hosein Group Title

why gave me medal i can't solve your ques

53. Shayaan_Mustafa Group Title

well i am going. good luck every one. take care.

54. heena Group Title

hey medal is not for only those who solve the ques but its for those too who atleast tries to solve it ok

55. heena Group Title

and i think u deserve as u given ur precious time to had a luk a my ques and tries it to solve as a help thnk you so much

56. hosein Group Title

this medal have not a value,i think however thanks for your attention sorry my english not well

57. heena Group Title

np i apreciate everyones work they did for helping others dats the main moto to give medals atleast people help others for medals.. and dnt think u dont solve dis medal is for ur work out in this ques ok..