The correct answer is: (i) and (ii) are correct.
Rolling resistance is the force that opposes the motion of a wheel rolling on a surface. It is caused by the deformation of the wheel and the surface as they come into contact. The amount of rolling resistance depends on a number of factors, including the weight of the vehicle, the slope of the road, and the condition of the road surface.
The weight of the vehicle is the most important factor in determining rolling resistance. The heavier the vehicle, the more force is required to overcome the deformation of the wheel and the surface. The slope of the road also affects rolling resistance. When the road is uphill, the vehicle has to overcome the force of gravity in addition to the rolling resistance. The condition of the road surface also affects rolling resistance. A rough or uneven surface will create more friction and therefore more rolling resistance.
The following are the explanations of each option:
- Option (i): Vehicle load. This is correct because the heavier the vehicle, the more force is required to overcome the deformation of the wheel and the surface.
- Option (ii): Grade. This is correct because when the road is uphill, the vehicle has to overcome the force of gravity in addition to the rolling resistance.
- Option (iii): Ground conditions. This is correct because a rough or uneven surface will create more friction and therefore more rolling resistance.