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Blazing goIITian

Joined:	19 Mar 2007
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15 Apr 2008 17:11:03 IST

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574

easy question on mirror (rates assured).................................

None

An object is placed at a distance of 20 cm from a convex mirror of focal length 20 cm. If the object is made to move away from the mirror with a speed of 5 cm/s, find the speed of image with respect to pole of the mirror.

plz justify ur answer as well.

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Comments (9)

ashish banga

Blazing goIITian

Joined: 16 Dec 2006

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15 Apr 2008 17:24:31 IST

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is the answer 0.01cm/s towards the mirror

pardesi .svk

Scorching goIITian

Joined: 7 Dec 2007

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15 Apr 2008 17:25:18 IST

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the ost cud have been less colourful
just use the formula 1/v + 1/u=1/f and diff both sides with respect to t

Tanmay

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15 Apr 2008 17:29:05 IST

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ya differentiate the equation

Karan Singh

Blazing goIITian

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15 Apr 2008 17:30:10 IST

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how ???

ashish banga

Blazing goIITian

Joined: 16 Dec 2006

Posts: 1362

15 Apr 2008 17:31:07 IST

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tell me if my answer is correct

Karan Singh

Blazing goIITian

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15 Apr 2008 17:38:15 IST

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i get the answer as 1 cm/s away from mirror.

ashish kindly check ur answer as it will definitely be away form mirror as when obj is at infinity , image is at focus.

c'mon guys ?
\
the procedure

Karan Singh

Blazing goIITian

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15 Apr 2008 17:41:52 IST

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i would like to enquire if the above question can be solved without calculus................??????????????

Tanmay

Blazing goIITian

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15 Apr 2008 17:55:58 IST

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f is constant

so we get

-1/v^2*dv/dt=1/u^2*du/dt

so we get dv/dt=-v^2/u^2*du/dt

calculate v by formula

put the values n get d ans............................

Skrishnasharma

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Joined: 18 Apr 2008

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20 Apr 2008 17:51:37 IST

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answer is 0.01cm from convex mirror

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