I believe the correct answer is A) From crest to crest.
~Silver
Answer:
35.6 N
Explanation:
We can consider only the forces acting along the horizontal direction to solve the problem.
There are two forces acting along the horizontal direction:
- The horizontal component of the pushing force, which is given by

with 
- The frictional force, whose magnitude is

where
, m=8.2 kg and g=9.8 m/s^2.
The two forces have opposite directions (because the frictional force is always opposite to the motion), and their resultant must be zero, because the suitcase is moving with constant velocity (which means acceleration equals zero, so according to Newton's second law: F=ma, the net force is zero). So we can write:

YES, ELECTRICITY CONCERNS ENERGY WHICH IS USED AS A FUEL . IN MODERN DAY TECH, MOST MACHINES USE ELECTRICITY AS A FUEL SUCH AS THE ELECTRONIC TRAIN IN TOKYO, JAPAN.