In an experiment, identical objects are placed on a glass slab, and a piece of sandpaper, as shown in the image. one end of both surfaces is raised 100 mm and the objects placed on them are observed. the ends are raised in increments of 100 mm until one of the objects begins to move. what does this experiment demonstrate? a) friction depends on the surface. b) friction is independent of the surface. c) friction is applicable to tilted surfaces only. d) friction depends on the object more than the surface.

Im not positive but i think the answer is A

Friction depends on the surface

This is the answer of your question

W= fd
where f is an applied force and d is the distance over which it is applied. when a parachuting skydiver is at constant velocity, he is experiencing "terminal velocity", the point at which his acceleration down is canceled out by air resistance. that means that the resisting force of the air is equal to his weight, but in the opposite direction. with this, we can solve for the work done by the force.
w = fd
w = (92.0)(9.81 m/s^2) (325)
w= 2.93 x 10^5 j
the value for work in this case is positive because it is pushing up on the skydiver, who has a downward force of gravity.
therefore the answer is 2.93 x 10^5 j