In which of the following situations is work NOT being done?* A table is dropped onto the ground. A chair is lifted vertically with respect to the floor. A stack of books is carried at waist level across a room. A bookcase is slid across carpeting.

In which of the following situations is work NOT being done?* A table is dropped onto the ground. A chair is lifted vertically with respect to the floor. A stack of books is carried at waist level across a room. A bookcase is slid across carpeting.