Lester prepares to lift a heavy sack of flour into a customer’s shopping cart. During which part of the action does Lester do work?

Work is done when a force causes an object to move in the direction of that force. As Lester lifts the sack from the floor to his chest, he applies an upward force while the sack moves upward. Holding it still involves no displacement, so choice D, “as he lifts the sack to his chest from the floor,” is correct.

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