Is the Driving Resistance Greater or Smaller on Downhill Sections?
3 Answers
Driving resistance on downhill sections is smaller compared to flat sections. On downhill sections, due to the effect of gravity, the driving resistance is reduced, making it easier for the vehicle to speed up and harder to control compared to driving on flat terrain. Increased driving resistance manifests as insufficient power during driving, a mismatch between speed and gear, increased fuel consumption, and poorer coasting performance when the vehicle is in neutral on straight roads. Reasons for increased driving resistance include: 1. Faults in the vehicle's transmission system: Poor lubrication, insufficient, deteriorated, or overly viscous lubricants in the drive axle's main reducer, differential, or transmission can increase driving resistance; improper assembly or adjustment of the drive axle's main reducer and transmission, overly tight bearing assembly, improper driveshaft assembly, overly tight or poorly lubricated universal joint bearings, or lack of oil; excessively small gear meshing clearance in the transmission increases transmission resistance, deformation of the drive axle housing, bending deformation of the half-shaft, and friction between the half-shaft and the half-shaft sleeve can all contribute to increased driving resistance. 2. Faults in the vehicle's driving system: Deformation or displacement of the front axle or drive axle can increase driving resistance; poor lubrication, deteriorated or insufficient lubricants in the wheel hub bearings, insufficient tire pressure, and deformation of the vehicle frame can all lead to increased driving resistance. 3. Overloading the vehicle, poor road conditions, and driving against the wind can also cause increased driving resistance.
When I frequently encounter downhill sections while driving, I feel the resistance is particularly low. The car naturally glides forward without me having to press the accelerator hard. Air resistance might still be there a bit, but overall, the engine burden is lighter, making the ride smoother. Gravity helps push the car downhill, reducing the pressure to fight resistance, much like cycling downhill—effortless and smooth. Especially during long trips, downhill sections save a lot of fuel, and I just need to control the brakes to avoid excessive speed. However, if the slope is too steep, I must be wary of uncontrolled acceleration and should downshift early or use engine braking. In short, with less resistance downhill, driving becomes more enjoyable.
From the perspective of automotive physics, the resistance indeed decreases when going downhill. The component of gravity pulls downward along the slope, helping to overcome part of the forward resistance, such as rolling resistance and air resistance. This allows the vehicle to move or even accelerate on the slope with less power required. However, if the speed is too high, wind resistance will increase, leading to energy loss. On a downhill slope, the net force is more favorable for motion, so the resistance is generally lower. This is beneficial for fuel efficiency, but it's important to balance engine output and brake usage while driving. I would recommend that beginners take advantage of downhill slopes to save energy while paying attention to speed control.
