14 What About Stairs?When you walk up stairs, work is done. Coming down the stairs, not so much.
15 Ladders are Inclined Planes Too When climbing a ladder, the horizontal distance travelled doesn’t count; only the vertical distance is used for work calculations.
16 StairsWalking up stairs requires work for the vertical portion. To walk downstairs requires no work becasue the direction of travel is the opposite of the direction of our upward force. Walking down stairs is “controlled falling”; it has the same net effect as falling, without the injuries.