* Net Force: An object's motion is determined by the net force acting on it. This is the vector sum of all the forces acting on the object.
* Balanced Forces: If the forces acting on an object are balanced, meaning they cancel each other out, the net force is zero. In this case, the object will remain at rest if it was at rest, or continue moving at a constant velocity if it was already moving.
Example:
Imagine a heavy box sitting on a table.
* Gravity: The force of gravity is pulling the box downwards.
* Normal Force: The table is pushing back on the box with an equal and opposite force.
These forces are balanced, resulting in a net force of zero. The box remains at rest.
Key Concepts:
* Newton's First Law of Motion (Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
* Newton's Second Law of Motion: The acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass.
Therefore, only unbalanced forces result in a change in an object's motion (either starting, stopping, or changing direction).
