Whenever you push an object across a frictional surface, it starts out taking a lot of force to push to get the object moving. However, once the object starts moving, it is much easier to keep it moving. What does this tell you about one of the main differences between static and kinetic friction? A) Static friction only depends on the surface material, while kinetic friction only depends on the motion
B) Kinetic and Static friction are the exact same thing
C) Static friction and kinetic friction are combined in one at all times, but static friction is just not seen during the motion
D) Static Friction is much stronger than kinetic friction, so it takes more force to get an object moving than it does to keep it moving

The correct answer is D. Static friction is much stronger than kinetic friction, so it takes more force to get an object moving than it does to keep it moving.

Explanation:

We can eliminate choice A if we know that both static friction and kinetic friction depend on what are called the coefficients of static friction and kinetic friction, respectively.  These coefficients are a reflection of the nature of the surface.  In other words, both static friction and kinetic friction depend on the surface material (choice A is incorrect).

Choice B is incorrect because static friction applies to still (static) object whereas kinetic friction applies to moving objects (that have kinetic energy).

Choice C is also incorrect.

Choice D is correct as described in the given information.  It takes much more force to start an object from rest than to keep it moving.  Think about things in your everyday life - it takes a push to get a toy car moving along the ground, but you do not need to consistently push the car with the same force to keep it moving.  This reflects that static friction is much stronger than kinetic friction, which is also described by the relationship between their coefficients (the coefficient of static friction is generally greater than that of kinetic friction).

Hope this helps!