# Surface friction and Newton's third law [duplicate]

My question is regarding a specific case displaying Newton's third law.

In the diagram below, a man is shown exerting a force on the wall, which in turn causes an equal and opposite reaction force on the man. I understand that the reason the man doesn't fly backwards is due to friction with the ground - the man exerts an action force on the ground which causes a reaction force back on the man. Hence, there is a 0 net force acting on the man as the original reaction force from the wall cancels out the reaction force from the ground. I am not confused about how objects move in general with respect to the third law since i understand that the action and reaction forces act on two separate objects. However, the logic behind this specific example would suggest that nothing on a plane would be able to move when a force is applied, since the friction from the ground would result in a 0 net force on the object.

For example, in the diagram shown below, a hand is exerting an action force on the brick. This in turn causes the brick to exert an action force on the floor which causes a reaction force on the brick. The action force on the brick and the reaction force on the brick exerted by the floor cancel each other out resulting in a 0 net force on the brick. Hence, the brick (or any other object on a plane like this) should not move and accelerate no matter how large a force is supplied. However, we are clearly able to push objects like bricks across a surface like a table in real life. I don't understand how this could be achieved as my understanding tells me that you cannot ever overcome the frictional force of the floor.

• What makes you think that the reaction force from the ground has to match the action force from the hand? – Chet Miller Dec 25 '18 at 13:24
• The action force on the brick from the hand causes an action force on the ground. Then, the ground will exert an opposite and equal reaction force back on the brick. – weary27 Dec 25 '18 at 13:37