Work done by the person:
is positive when lifting the box
is negative when lowering the box
Fg m g
1 s
Work done by the gravity:
is negative when lifting the box
is positive when lowering the box
Example 2: then moving it horizontally
2 s
11
Example 2: … then moving it horizontally
Work done by the person and gravity:
i h i it h i t ll 11 is zero when moving it horizontally