Answer: Option (d) is the correct answer.
Explanation:
Net force means the sum of total or all the forces acting on an object.
Mathematically, \(F_{total} = F_{1} + F_{2} + F_{3} +\) ....and so on
Therefore, when a boy is pushing a chair by applying a force of 5 newtons and his mother is helping him by pushing the chair with a force of 7 newtons then calculate the net force acting on the chair as follows.
\(F_{total} = F_{1} + F_{2}\)
= (5 + 7) N
= 12 N
Thus, we can conclude that net force acting on the chair is 12 N.
