The relationship between object distance, image distance, and focal length of a spherical mirror is given by
1/f=1/v+1/u
Where
f= focal length of a spherical mirror (distance between the pole and the principal focus of the mirror)
u= object distance (distance between pole and object)
v= image distance (the distance between pole and image)
The pia mater<span> is the innermost layer of the meninges and attaches directly to the brain and spinal cord.</span>
Forces are considered balanced when all of the combined forces lead to no change in the motion of the object. For example, when a book is sitting on a table, the force of gravity is pushing downward and the normal force is pushing upward with exactly the same amount of force. Since they are equal and opposite forces, the book does not move.
Unbalanced forces exist when there are unequal forces acting upon the object, which leads to a change in the state of motion. Unbalanced forces can lead to a change in direction, a change in speed, or both a change in direction and in speed.
