Understanding Resistive Force and Rolling Resistance

The question asks to identify the specific name for the resistive force that acts between a vehicle's tyres and the road surface.

Let's look at the options provided:

• Rolling resistance: This is a force that resists the motion when an object rolls on a surface. It is primarily caused by the deformation of the object and the surface at the point of contact. For a vehicle's tyre rolling on a road, the tyre deforms slightly as it rolls, and the road surface might also deform slightly. This deformation leads to energy loss, which manifests as a resistive force opposing the rolling motion.
• Earthing resistance: This term is related to electrical engineering and refers to the resistance of the path of an electric current from an appliance or system into the ground. It has nothing to do with the mechanical force resisting motion between a tyre and a road.
• Tyre resistance: While the tyre itself contributes to rolling resistance due to its material properties and construction, "Tyre resistance" is not the standard technical term for the force opposing rolling motion on a surface. It is too vague.
• Road resistance: This term is also too general. Road resistance could encompass various factors that oppose a vehicle's motion, such as air resistance, rolling resistance, and possibly even uphill gradients. It is not specific to the force between the tyre and the surface.

Based on standard physics and engineering terminology, the resistive force between a vehicle's tyres and the road, which opposes the rolling motion, is specifically called rolling resistance.

Therefore, the correct answer is Rolling resistance.

Detailed Explanation of Rolling Resistance

Rolling resistance, also known as rolling friction or rolling drag, is the force resisting the motion when a body rolls on a surface. It is mainly caused by the deformation of the rolling object (like a tyre) and the surface it rolls upon. When a tyre rolls, the area in contact with the road is not a single point but an area (contact patch). As the tyre rotates, the material within this contact patch is constantly being deformed and then recovering. This deformation and recovery process is not perfectly elastic, leading to energy dissipation (loss of energy as heat), which results in a force opposing the rolling motion.

Factors affecting rolling resistance include:

• Tyre pressure (lower pressure means more deformation)
• Tyre material and construction
• Tyre size
• Road surface type and condition (rougher surfaces generally have higher rolling resistance)
• Vehicle speed (though less significant than air resistance at high speeds)
• Load on the tyre (higher load generally means more deformation and higher resistance)

Comparing Resistive Forces

It's important to distinguish rolling resistance from other resistive forces a vehicle experiences:

• Rolling Resistance: Force between tyre and road surface opposing rolling. Primarily due to deformation.
• Aerodynamic Drag (Air Resistance): Force opposing motion through the air. Increases significantly with speed ($\text{Drag} \propto v^2$).
• Gradient Resistance: The component of gravity acting against motion when moving uphill. Depends on the vehicle's weight and the slope angle ($\text{Resistance} = \text{Weight} \times \sin(\text{angle})$).

The force specifically acting to resist the rolling motion at the interface between the tyre and the road is indeed Rolling resistance.

Revision Table: Key Concepts

Additional Information: Tyre-Road Interaction

The interaction between the tyre and the road is crucial for vehicle performance, including acceleration, braking, and cornering, in addition to rolling resistance. While rolling resistance opposes the rolling motion, the grip (static or kinetic friction) between the tyre and the road allows the vehicle to move forward (propulsion) or slow down (braking).

Rolling resistance is generally much smaller than the maximum available static friction force between the tyre and the road, which is what allows the car to accelerate. However, minimizing rolling resistance is important for fuel efficiency, especially at lower speeds where it can be a significant component of the total resistive force.