mass = 5kg
acceleration due to gravity = 9.8 m/s²
Notice that we only have to work with vertical components,
__Fn = ma (normal force Manuel exerts on box) (upward direction)
__Fw = mg (weight of box) (downward direction)
Because there is no change in motion, the sum of the vertical components should be equal to 0 or balance each other out. Therefore,
ΣFy = Fn + (-Fw)
0 = Fn + (-mg) [solve for Fn]
mg = Fn
(5kg)(9.8m/s²) =
49 N = Fn = Force that Manuel is exerting on box (upward direction)