Hi there!
We know that there are TWO forces acting on the man.
- Force due to gravity: Acts DOWNWARD
- Normal force due to the elevator floor: UPWARD
We can express this in an equation. Let DOWN be NEGATIVE, and UP be POSITIVE.
[tex]F_{net} = N - F_g[/tex]
Recall that a SCALE measures the NORMAL FORCE, NOT the WEIGHT. Therefore:
N = 700 N
W = 900 N
[tex]F_{net} = 700 - 900 \\\\F_{net} = -200N[/tex]
Since downward is negative, the net force is acting DOWNWARD.
