What type of resistance is primarily due to the flexing of tires and penetration of the surface?

Rolling resistance is the correct answer because it refers specifically to the energy loss that occurs when a tire rolls over a surface. This type of resistance arises from the deformation of the tire as it contacts the ground and the flexing that occurs as it rotates. The rolling tire compresses and elongates, which requires energy to maintain its motion against the frictional forces at the tire-surface interface.

In the context of transportation and vehicle dynamics, rolling resistance plays a crucial role in determining fuel efficiency and overall vehicle performance. Factors that influence rolling resistance include tire pressure, tire material, surface texture, and the weight of the vehicle. Understanding this type of resistance is essential for engineers and professionals in the field of sanitary engineering and transportation, as it impacts the design and operational efficiency of vehicles.

Other types of resistance mentioned, such as grade resistance, relates to the incline of the road and the effects of gravity on the vehicle, while dynamic and static resistance are generally more associated with forces involved in motion and inertia, rather than the specific deformation associated with tire flexing and surface interaction.