Which factor primarily affects the grade resistance of a vehicle?

The grade resistance of a vehicle is primarily affected by the angle of the inclined surface on which the vehicle is traveling. Grade resistance is the force that opposes the motion of a vehicle when it is moving uphill or downhill, and it depends on the slope of the incline. When the angle of the incline increases, the vertical component of the gravitational force acting on the vehicle also increases, which in turn increases the grade resistance experienced by the vehicle.

If a vehicle is on a steep incline, it must exert more force to overcome the increased gravitational pull acting against it, thus making the angle of the inclined surface a critical factor in determining grade resistance.

While the weight of the vehicle and the type of load can influence the total force required to move the vehicle, the specific concept of grade resistance is directly tied to how steep the incline is. The speed of the vehicle does not directly affect grade resistance; instead, it could affect the overall performance and energy consumption of the vehicle but does not change the resistance due to the slope.