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A string connected with bob is suspended...

A string connected with bob is suspended by the point (O) such that it sweeps out conical surface in horizontal plane. Here `vecr` is the position vector of bob `vecc` is its velocity and `vecz` is the axis of swept cone as shown. Select INCORRECT statement :-

A

`vecr.vecz` is always zero

B

`vecr.vecv` is always zero

C

`vecz.vecv` is always constant

D

`vecr.vecz` is always non zero constant

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The correct Answer is:
A
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