Why do lorries use more energy when travelling fast?

Lorries use more energy when traveling fast due to increased air resistance, or drag, which rises exponentially with speed. As a vehicle moves faster, it must exert more power to overcome this resistance, leading to higher fuel consumption. Additionally, at higher speeds, the engine operates less efficiently, further contributing to greater energy use. Overall, the combination of aerodynamic drag and engine inefficiency at high speeds results in increased energy expenditure for lorries.