We call a description of where something is located a position vector. Now let's define more precisely speed and velocity. Two cars moving with the same speed do not necessarily have the same velocity. One could be traveling north and the other south. We use boldface to indicate vectors or arrows over the quantity.
Acceleration can be due to a change in speed or a change in direction.
Circular motion at constant speed is called centripetal acceleration . Inertia is the property of a body that causes it to remain at rest or in motion unless acted upon by an outside force. A body remains at rest or continues in uniform motion except when compelled to change its motion by forces acting upon it. Also called the law of inertia. A force is a push or pull.