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Energy is being expended maintaining it in position. Earth's gravity is applying a force downwards, the book is being accelerated down gravitation force.

A force is being applied to the hand and arm which must be resisted and thus energy expended.

The arm and book are not a closed system.

Energy is being expended maintaining it in position. Earth's gravity is applying a force downwards, the book is being accelerated down.

Energy is being expended maintaining it in position. Earth's gravity is applying a force downwards, the book is being accelerated down gravitation force.

A force is being applied to the hand and arm which must be resisted and thus energy expended.

The arm and book are not a closed system.

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Energy is being expended maintaining it in position. Earth's gravity is applying a force downwards, the book is being accelerated down.