|MLA Citation:||Bloomfield, Louis A. "Question 1479"|
How Everything Works 13 Dec 2017. 13 Dec 2017 <http://howeverythingworks.org/print1.php?QNum=1479>.
But when you carry the sack horizontally at a steady pace, the upward force you exert on the sack and the horizontal distance it travels are at right angles to one another. You don't do any work on the sack in that case. The evidence here is that the sack doesn't become any more dangerous; its speed doesn't increase and neither does its altitude. It just shifts from one place to an equivalent one to its side.