How much does it cost to stop a car from 80 km/h?
Every driver experiences this almost daily: another vehicle, bike, or pedestrian crosses your driving trajectory, forcing you to brake. Assuming an average European car weighs about 1400 kg and is moving at 80 km/h, its kinetic energy is (m * v^2 / 2 =) 346 kJ. The gasoline volumetric energy density is 34.8 MJ/L, but considering a not-so-conservative estimate of the engine efficiency of 30%, means that the motor transforms 1 L of gasoline in heat and (34.8 * 30% =) 10.2 MJ of useful energy. This means that to accelerate our average 1.4-ton car to 80 km/h the engine uses (346 kJ / 10.2 MJ/L ≈) 0.034 L of gasoline.
With the current (2021) gasoline price of 1.75 €/L, to accelerate to 80 km/h it costs about (1.75 €/L * 0.034 L ≈) 0.06 €.