In the given example, there are three forces acting on the object, which is the monkey pulling herself up on a tree branch using both arms:
The force of gravity: This force is pulling the monkey down towards the ground. The weight of the monkey and the force of gravity are acting in the downward direction.
The force exerted by the monkey on the tree branch: As the monkey pulls herself up on the tree branch using both arms, she is exerting a force on the branch in the upward direction. This force is also known as the tension force, as it is caused by the tension in the monkey's arms and the resistance of the branch.
The reaction force exerted by the tree branch on the monkey: According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction. As the monkey exerts a force on the tree branch, the branch exerts an equal and opposite force on the monkey, pushing her upward.
Therefore, the three forces acting on the object, which is the monkey pulling herself up on a tree branch using both arms, are the force of gravity pulling the monkey down, the tension force exerted by the monkey on the tree branch pulling her upward, and the reaction force exerted by the tree branch on the monkey pushing her upward.