Question

why is it always harder to start to move an object that is initially at rest across a horizontal surface than it is to keep that same object moving?
a the static friction between two surfaces is always greater than the kinetic (sliding) friction between the same two surfaces.
b the amounts of static friction and kinetic (sliding) friction must add up to cause the object to accelerate.
c an object that is at rest has more inertia than an object that is moving.
d the lack of a normal force once the object is moving requires less effort.
e the static friction and kinetic (sliding) friction are always equal in size and opposite in direction.

Explanation:

Static friction resists initial motion and is greater than kinetic friction which acts during motion. Once the object is moving, less force is needed to overcome kinetic friction.

Answer:

A. The static friction between two surfaces is always greater than the kinetic (sliding) friction between the same two surfaces.