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Asseration : A plank A is placed on a ro...

Asseration : A plank A is placed on a rough surface over which a block B is placed. In the shown situation, elastic cord is unstretched. Now a gradually increasing force F is appled slowly on A until the relative motion between the block and plank starts.
.
At this moment cord is making an angle` theta` with the vertical. Work done by force F is equal to energy lost against fricton `f_(2)`, plus potential energy stored in the cord.
Reason : work done by static friction `f_(1)` on the system as a whole is zero.

A

If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.

B

If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion.

C

If Assertion is true, but the Reason is false

D

If Assertion is false but the Reason is true.

Text Solution

Verified by Experts

The correct Answer is:
A
`(W_(f1))_(on A) = - f_(1) s`
`(W_(f1))_(on B) = - f_(1) s`
`:.` Net work done by `f_(1) =0`
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