Author Topic: All Mechanics DOUBTS HERE!!!  (Read 87915 times)

Offline halosh92

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Re: All Mechanics DOUBTS HERE!!!
« Reply #60 on: May 15, 2010, 10:30:27 pm »
edexcel
jan 2005 Q5b
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline cooldude

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Re: All Mechanics DOUBTS HERE!!!
« Reply #61 on: May 16, 2010, 06:19:51 am »
edexcel
jan 2005 Q5b

cud u please post the link of the paper as i'm not familiar with edexcel so i might end up solving the wrong question.

Offline halosh92

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Re: All Mechanics DOUBTS HERE!!!
« Reply #62 on: May 16, 2010, 08:06:34 am »
cud u please post the link of the paper as i'm not familiar with edexcel so i might end up solving the wrong question.
everyday we wake up is a miracle, then how do we say miracles dont happen?????

Offline cooldude

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Re: All Mechanics DOUBTS HERE!!!
« Reply #63 on: May 16, 2010, 08:38:13 am »


a=3.2
for the 0.8 kg mass---->
8-T=0.8a
8-T=0.8*3.2
T=5.44 N

Offline melony

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Re: All Mechanics DOUBTS HERE!!!
« Reply #64 on: May 16, 2010, 06:26:09 pm »
Quote
Insert Quote
edexcel
jan 2005 Q5b

There you go! ;D
xOx

Offline Fenomenoe9

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Re: All Mechanics DOUBTS HERE!!!
« Reply #65 on: May 16, 2010, 07:08:20 pm »
GUys Please this question is messing with me i dont get even what it means. PLease Help.

It's 2007 January Q7 part (f).

Appreciate the help peace..

Offline Fenomenoe9

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Re: All Mechanics DOUBTS HERE!!!
« Reply #66 on: May 16, 2010, 07:14:21 pm »
here m and thanks

Offline Fenomenoe9

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Re: All Mechanics DOUBTS HERE!!!
« Reply #67 on: May 16, 2010, 07:15:39 pm »
here m and thanks oh yahh the answer is 0.51s

Offline cooldude

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Re: All Mechanics DOUBTS HERE!!!
« Reply #68 on: May 16, 2010, 07:29:14 pm »
here m and thanks

okay for this basically u find out the time the for P to come to rest and then double that value---.
as the string is now slack for this period there is no tension in the string so the deceleration of P will be-->
F=ma, -30sin30=3a
a=-10sin30=-5
the time taken for Q to reach the ground is-->
0.8=0.5*0.98*t^2
t=1.28 sec
therefore final speed of P=
v=0+(1.28*0.98)
v=1.24 m/s
0=1.24-5t
t=0.248 sec
this is the time P takes to come to rest therefore the time for it to become taut again will be double that=0.248*2=0.496 sec, By the way there might be some inaccuracies in the final answer as i did not use exact values


Offline cooldude

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Re: All Mechanics DOUBTS HERE!!!
« Reply #69 on: May 16, 2010, 07:32:05 pm »
okay for this basically u find out the time the for P to come to rest and then double that value---.
as the string is now slack for this period there is no tension in the string so the deceleration of P will be-->
F=ma, -30sin30=3a
a=-10sin30=-5
the time taken for Q to reach the ground is-->
0.8=0.5*0.98*t^2
t=1.28 sec
therefore final speed of P=
v=0+(1.28*0.98)
v=1.24 m/s
0=1.24-5t
t=0.248 sec
this is the time P takes to come to rest therefore the time for it to become taut again will be double that=0.248*2=0.496 sec, By the way there might be some inaccuracies in the final answer as i did not use exact values

take t as 4root5/7 sec and ull get the exact answer


Offline Fenomenoe9

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Re: All Mechanics DOUBTS HERE!!!
« Reply #70 on: May 16, 2010, 07:43:56 pm »
ok but why does the time taken for P to rest double?

Offline astarmathsandphysics

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Re: All Mechanics DOUBTS HERE!!!
« Reply #71 on: May 16, 2010, 07:48:33 pm »
cos it has to travel the same distance with the same acceleration - motion in reverse

Offline cooldude

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Re: All Mechanics DOUBTS HERE!!!
« Reply #72 on: May 16, 2010, 07:49:22 pm »
ok but why does the time taken for P to rest double?

cuz c wen P reaches rest, Q is still incapable of movement as the string is still slack, but then when P goes back down the plane and when it reaches the point where it initially was i.e. 0.51 sec previously, the string becomes taut again and Q rises again, we double the time because we consider both the period when P travels up the plane and back down. P moves down the plane because of its weight, there is no other force acting on P as the tension in the string is non-existent for the duration of the time the string is slack, i.e. the interval of 0.51 sec, hope u get it.

Offline cooldude

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Re: All Mechanics DOUBTS HERE!!!
« Reply #73 on: May 16, 2010, 07:50:55 pm »
cos it has to travel the same distance with the same acceleration - motion in reverse

sorry sir, didnt notice you'd already answered   :-[

Offline Fenomenoe9

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Re: All Mechanics DOUBTS HERE!!!
« Reply #74 on: May 16, 2010, 07:54:26 pm »
haha i love u man thanks alot for helping and yeah i get it man, thanks again! bye