* A book resting on a table: Gravity pulls the book downwards, but the table exerts an equal and opposite normal force upwards. These forces cancel each other out, resulting in a net force of zero, and the book remains stationary.
* A person pushing against a wall: The person exerts a force on the wall, but the wall exerts an equal and opposite force back on the person. Since the forces are balanced, neither the person nor the wall moves.
* A magnet holding a metal object: The magnet exerts a magnetic force on the metal object, attracting it. However, if the object is heavy enough, the force of gravity might be stronger than the magnetic force, preventing the object from moving.
Key point: For an object to move, there needs to be a net force acting on it. This means the forces acting on the object must be unbalanced. If the forces are balanced, the object will remain at rest or continue moving at a constant velocity.
