A block of mass m is placed on a rough...

A block of mass m is placed on a rough floor of a lift . The coefficient of friction between the block and the floor is `mu`. When the lift falls freely, the block is pulled horizontally on the floor. What is the force of friction -

`mumg`

`mumg//2`

`2mumg`

Zero

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The correct Answer is:

Normal force at contact becomes zero.

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