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Mechanics

Blazing goIITian

Joined:	14 Jan 2007
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6 Apr 2008 19:53:36 IST

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361

Find friction

None

Hey,

A disc starts rotating with a constant angular acceleration 1rad/sec2 about a fixed vertical axis perpendicular to its plane through its centre.A coin of mas 10g is placed on the disc at a distance of 10cm from the axis.The coeffecient of friction between the disc and the coin is .2.The value of the frictional force on the coin a t=1s will be what?

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Karthik M

Blazing goIITian

Joined: 1 May 2007

Posts: 2830

6 Apr 2008 20:09:58 IST

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Hi!

Simple question.

angular velocity of the disc at t=1s = @t = 1x1 = 1rad/s.

Now, if the coin is to stay on the disc, centripetal force is to be provided by frictional force, hence:

f(t=1s) = .01 x 1 x .1 = .001N

ramyani chakrabarty

Blazing goIITian

Joined: 22 Apr 2007

Posts: 2537

6 Apr 2008 20:15:41 IST

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0.01

Karthik M

Blazing goIITian

Joined: 1 May 2007

Posts: 2830

6 Apr 2008 20:16:29 IST

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Note that the coefficient of friction given is superfluous data.

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