The net force on the chair is 100N
<u>Explanation:</u>
The free body diagram is attached below.
According to the condition,
when a downward gravitational force of 155N of earth acts then an equal opposite upward force of same magnitude also acts on the chair.
Therefore, the normal force acting on the chair is 155N
When a chair is pushed forward on a surface, then a frictional force also acts on it in opposite direction.
The net force acting on the chair is = F - f
Where,
F is the applied force
f is the force of friction
Net force = 155N - 55N
Fnet = 100N
Therefore, net force on the chair is 100N