Force:
A force is a push or pull that can cause an object to move, stop, or change its speed or direction. It is a vector quantity, meaning it has both magnitude and direction.

Balanced Forces:
Balanced forces are forces that are equal in size and opposite in direction. When balanced forces act on an object, the object remains at rest or continues to move at a constant velocity.

Unbalanced Forces:
Unbalanced forces are forces that are not equal in size and/or opposite in direction. When unbalanced forces act on an object, they cause the object to accelerate in the direction of the net force.

Inertia:
Inertia is the tendency of an object to resist changes in its motion. An object at rest will remain at rest, and an object in motion will continue moving at a constant velocity unless acted upon by an external force.

Newton's First Law of Motion:
Newton's first law of motion, also known as the law of inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This means that an object will not change its state of motion unless a force is applied to it. In other words, objects tend to maintain their current state of motion (either at rest or moving at a constant velocity) unless something outside of the object causes a change.