Mechanics - rotation

1

skygirl ·2009-03-26 08:16:28

two points to remember:-

1) after collision, direction of linear vel changes

2) ................., direction of angular velocity is same. [as wall is smooth]

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1

kamalendu ghosh ·2009-03-26 08:17:48

xactly..I did it in the same way...find the ans...

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62

Lokesh Verma ·2009-03-26 08:22:23

intially v=Ï‰r

after colission , v=-v, Ï‰=Ï‰

friction is Î¼R
a=Î¼g
Torque = Î¼mgr=2/5mr²Î±

thus, 5/2Î¼g=Î±r

Ï‰(t)=Ï‰-Î±t=Ï‰- 5/(2r) Î¼gt

v(t)=-v+Î¼gt

-v+Î¼gt=Ï‰r- 5/2Î¼gt

7/2Î¼gt=2v

Î¼gt=4/7v

thus at pure rolling veloctiy is

3/7v

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33

Abhishek Priyam ·2009-03-26 08:23:40

3m/s

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33

Abhishek Priyam ·2009-03-26 08:24:16

oh!! u posted...

:)

but conserving angular momentum is more easy...

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33

Abhishek Priyam ·2009-03-26 08:25:26

m7R-2/5mR²(7/R)=7/5mR²(v/R)

solving we get v=3m/s

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1

skygirl ·2009-03-26 08:33:30

intially v=Ï‰r

i too took this ...

but suddenly am feeling... its not told so in the question.....[12]

can we take it?

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33

Abhishek Priyam ·2009-03-26 08:36:24

sphere roll on....

so conventially it is pure rolling.. :P

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kamalendu ghosh ·2009-03-26 08:37:02

of course we can take it...... it is told that it is rolling initially...in the first few words ..

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