Your weight caused by gravity is pulling you down the floor is reacting by pushing back.
The force that the floor exerts on you is.
It can t go through the floor the normal force fn exerted by the floor equals the weight w plus the downward component of the applied force 38 sin 41 24 9.
The floor exerts a reaction force forward on the professor that causes her to accelerate forward.
Fn 150 24 9 174 9.
In the vertical direction the net force is zero since the velocity component in that direction must remain zero.
Therefore the baby does not plummet down the earth.
And it goes same for the fourth case.
The external force is the wire that pulls the elevator.
In order to walk on a floor or any other surface your foot must push backward on the floor action force so that the floor pushes you forward reaction force.
The force that your foot and the floor exert on each other is a friction force between the sole of your shoe and the floor.
We call this force the reaction force.
Newton s third law states that every action has an equal and oposite reaction you may not think this but when you re standing ont he floor you are excerting a force against the floor.
True when you jump you accelerate upward because the floor exerts an upward force on you.
It discusses how to calculate the apparent weight.
Newton s first law states that if all the forces cancel each other out.
The actual normal force comes from the floor of the elevator exerting the same force as the baby s weight force which follows newton s third law.
This physics video tutorial explains how to find the normal force on a scale in a typical elevator problem.