Author Topic: FRICTION !!!!!!!! HELP!!!!  (Read 5343 times)

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #30 on: November 03, 2009, 09:01:53 am »
for the 1st
>2T root 3  /2-Troot 3 /2=ma  so Troot 3 /2=ma m=maa osf ball
res vertically 2T/2+T=mg so T=2mg/3
then from first eq a=2mg/3 *root 3 /2m=groot 3 /3 =

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #31 on: November 03, 2009, 09:17:18 am »
working back for the secon one I get the acceleration of the bead is 7g/4 which is impossible

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #32 on: November 03, 2009, 09:25:12 am »
I can see the problem now. As the bead is moving down the string., the string is accelerating upwards so the length of time will be shorter. I have to find the acceleration of the m particle

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #33 on: November 03, 2009, 10:01:26 am »
I think I have it. Solve the equations a1+a2=g
and a2=g/4 to get a1=3g/4 then string is passing through bead at 2a1+a2=7g/4 and use s=1/2at^2 with a =7g/4

nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #34 on: November 03, 2009, 01:27:01 pm »
THank YoU Very MucH Sir

nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #35 on: November 04, 2009, 03:27:10 pm »
Need help again :(

Find the acceleration of the wedge shown in the figure if the mass of the wedge is 4 times the mass of the block. All surfaces are frictionless. The angle of the inclined surface of the wedge is 37o with the horizontal.

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #36 on: November 04, 2009, 03:30:54 pm »
It will be late tonight when i answer this.

nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #37 on: November 04, 2009, 03:36:11 pm »
It will be late tonight when i answer this.

np :)

nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #38 on: November 04, 2009, 03:42:57 pm »
Well I'd have to add a few more to this ::) I'm dumb u c :D


In the figure shown,pulley and strings are light and inextensible.Initially all the bodies are at rest when string connecting A and B is cut. Find the initial acceleration of A,C and the pulley


nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #39 on: November 05, 2009, 03:33:50 am »
Anybody give it try plzz.....

Offline 123

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #40 on: November 05, 2009, 04:02:49 am »
hey nid about that wedge n block.....heres what i did wit my m1 knowledge n a lil thinkin  :P


Since all surfaces r frictionless, the wedge resting on ground would slip as the block moves down. So i guess v need to split the component of block's weight (4mg) into a force pushing the wedge... so that it slips left
I don't think this is the right way...mayb astar can help
Interestin ques...even i wanna know the answer  :D

did u ask in goiit.com?


nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #41 on: November 05, 2009, 04:04:26 am »
Thanks for givin it a try :)

I saw that site. I registered but I'm still to ask questions there....thanks a lot tho :D

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #42 on: November 05, 2009, 11:43:13 am »
For the pulley when the string is cut there is a resultant for ce mg due to the tension in the spring acting on a total mass of 3m hence using F=ma
mg=3ma so a =g/3
(The tension initially is 4mg becasue`the system is in equilibrium)

resolving vertically for A
T-mg=ma
and for B
2mg-T=2ma
solve these to get a=g/3
so the acceleration of A is g/3+g/3=2g/3 and the acceleration of B is g/3-g/3=0

Offline astarmathsandphysics

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #43 on: November 05, 2009, 12:15:41 pm »
For the black and wedge problem try this attachement

nid404

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Re: FRICTION !!!!!!!! HELP!!!!
« Reply #44 on: November 05, 2009, 02:36:45 pm »
thanks sir... :)